Maturity Structure andSupply Factors in Japanese
Government Bond Markets
Ichiro Fukunaga, Naoya Kato, and Junko Koeda
Using our constructed database on the amount outstanding of Japanese
Government Bonds (JGBs) categorized by holder and remaining maturity,
we examine the eﬀects of changes in the holders and maturity structureson the term structure of interest rates and the risk premium on long-termbonds. Both approaches using single-equation regressions and a term
structure model confirm that the net supply of JGBs, the issuance (supply)by the government minus the demand by the preferred-habitat investors
including the Bank of Japan (BOJ), had significant eﬀects on long-term
interest rates. The regression approach implies that the net supply eﬀects
were stronger in the zero interest rate periods, while this relationship was
not found using the model approach. We also calculate the net supply
eﬀects of the BOJ’s JGB purchases as part of its Quantitative and Qualitative Monetary Easing and compare the results with those obtained froma simple event-study analysis.
Keywords: Japanese Government Bonds; Term structure of interest rates;
Preferred habitat; Unconventional monetary policy
JEL Classification: E43, E44, E52, E58, G11, G12, H63

Ichiro Fukunaga: Director and Senior Economist, Institute for Monetary and Economic Studies,Bank of Japan (currently International Monetary Fund, E-mail: ifukunaga@imf.org)
Naoya Kato: Associate Director, Institute for Monetary and Economic Studies (currently Research and Statistics Department), Bank of Japan (E-mail: naoya.katou@boj.or.jp)
Junko Koeda: Associate Professor, School of Political Science and Economics, Waseda University (E-mail: jkoeda@waseda.jp).....................................................................................................................
The authors would like to thank Kazuo Ueda, Christopher Waller, the participants at the 2015
BOJ-IMES Conference, and the staﬀ at the Bank of Japan, for their helpful comments. Takako
Yoshiba helped to prepare the data. The views expressed in this paper are those of the authorsand do not necessarily reflect the oﬃcial views of the Bank of Japan.

MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015
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45

I. Introduction
After the recent global financial crisis, many central banks in advanced economies
lost their conventional monetary policy tools near the zero lower bound on short-term
interest rates. To provide further monetary accommodation, they have moved to unconventional tools, such as forward guidance and government bond purchases, aimed
at aﬀecting longer-term interest rates.1 The Bank of Japan (BOJ) introduced these unconventional tools long before the global financial crisis,2 but since April 2013, it has
implemented more aggressive monetary easing measures, the “Quantitative and Qualitative Monetary Easing (QQE),” to overcome prolonged deflation and achieve the pricestability target.3 Under the QQE, the pace of the BOJ’s purchases of Japanese Government Bonds (JGBs) has accelerated and the remaining maturity of its JGB purchases
has been extended significantly, while clear forward guidance on the continuation of
the policy has been provided.
In general, a central bank’s purchases of government bonds are considered to lower
long-term interest rates through three channels: the signaling channel, the scarcity
channel, and the duration channel.4 The signaling channel captures the role of bondpurchases as a credible commitment by the central bank to keep interest rates low andthus serves as a complement to forward guidance. The bond purchases may support
the credibility because market participants may perceive that it would be diﬃcult forthe central bank to raise rates rapidly with a large amount of long-term assets on its
balance sheet. The scarcity channel captures the eﬀect of a shortage of bonds withparticular maturities available for trading, caused by the central bank’s purchase of
these particular bonds, on the corresponding yields. The duration channel captures adownward shift of the entire yield curve through a decrease in the price of duration risk
(risk premium) caused by the central bank’s purchases of longer-term bonds. Amongthese channels, the signaling channel had been considered to be the main channel until
recently. Theoretically, according to the expectations hypothesis, changes in the supply of bonds should aﬀect yields only to the extent that expectations of future shortterm interest rates are changed, that is, only through the signaling channel.5 Similarly,................................
1. Many central banks in advanced economies purchased private as well as public assets, especially in the earlier
part of the post-crisis period, mainly to restore the functioning of financial markets and intermediation rather
than provide monetary accommodation.
2. The BOJ first introduced a zero interest rate policy in 1999 after a domestic banking crisis, and then implemented a quantitative monetary easing policy from 2001 through 2006 with forward guidance on the continuation of the policy. After the global financial crisis in 2008, the BOJ again cut the policy rate to virtually zeroand established an asset purchase program under its “Comprehensive Monetary Easing.”
3. The BOJ’s price stability target was set at 2 percent in terms of the year-on-year rate of change in the consumer
price index in January 2013. Before that, the “price stability goal in the medium to long term” was set at 1
percent (in a positive range of 2 percent or lower). A crucial feature of the QQE is that it aims to raise inflation
expectations through a strong and clear commitment to achieving the price stability target as well as massive
purchases of JGBs, and thereby to lower real interest rates. In this paper, however, our analyses focus on
nominal rather than real interest rates. For an analysis of real interest rates and the inflation risk premia inJapan, see for instance Imakubo and Nakajima (2015).
4. This classification follows IMF (2013). Krishnamurthy and Vissing-Jørgensen (2011) classify the channels
through which the Federal Reserve’s quantitative easing policies aﬀected a broader range of long-term interest
rates, including the interest rates on corporate bonds and real interest rates. Joyce et al. (2012) survey thetheoretical and empirical literature on the transmission mechanisms of quantitative easing policies.
5. Gürkaynak and Wright (2012) discuss various implications and limitations of the expectations hypothesis and

46 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Eggertsson and Woodford (2003) argue that the central bank’s open-market operations
would be irrelevant if they did not change the expected future conduct of monetaryor fiscal policy. Empirically, at least for Japan, existing studies on the earlier quantitative easing policy imply that the eﬀects through the scarcity and duration channels,
often combined and referred to as the portfolio rebalance channel, were smaller or lessclear-cut than those through the signaling channel.6
Recent studies motivated by the implementation of large-scale bond purchasesby many central banks in advanced economies, however, pay more attention to thescarcity and duration channels. A theoretical background of the scarcity channel is thepreferred-habitat theory, first set forth by Modigliani and Sutch (1966), which assumes
that bond markets are segmented due to the existence of “preferred-habitat” investors
with preferences for particular maturities and thus the interest rate for a given maturity
is determined by the supply and demand of bonds with that particular maturity. Basedon this assumption, Vayanos and Vila (2009) construct a model of the term structure ofinterest rates in which the term structure and bond risk premia are determined throughthe interaction between the preferred-habitat investors and risk-averse arbitragers andthereby the duration channel generated by the arbitragers’ aversion to duration risk aswell as the scarcity channel is incorporated.7 Two important predictions of this theoretical framework are as follows: (i) the “net supply” of more and longer-term government bonds, which is defined as the issuance (supply) by the government minus thedemand by the preferred-habitat investors, leads to a higher risk premium and steeper
yield curve; and (ii) the above “net supply” eﬀects are stronger when the arbitragers’
risk aversion is higher. In the real world, the preferred-habitat investors include longterm investors such as pension funds and insurance companies as well as central banks
that implement large-scale bond purchases as an unconventional monetary policy tool.
The preferred-habitat theory can explain a variety of episodes in which a shock to the
net supply of government bonds aﬀected long-term interest rates,8 including the recent
bond purchases by central banks in advanced economies, and appears to be increasingly accepted by policymakers as well as academic economists.9
In this paper, we examine how the net supply of JGBs aﬀected the term structureof interest rates and the risk premium on long-term JGBs using Japanese monthly datafrom January 1992 to September 2014, which includes the period after the QQE wasintroduced.10 First we construct a database on the amount outstanding of JGBs categorized by holder and remaining maturity, from which various net supply measures are..........................................................................................................................................
standard aﬃne term structure models.
6. For details, see for instance Ugai (2007) and Ueda (2012a, c).
7. The model of Vayanos and Vila (2009) can be positioned within the literature on “limits of arbitrage” surveyed
by Gromb and Vayanos (2010) that investigates how costs faced by arbitragers, that is, shocks to the demandand supply of government bonds with particular maturities absorbed by the risk-averse arbitragers in thismodel, can prevent them from eliminating mispricings.
8. Greenwood and Vayanos (2010) present two recent episodes that strongly support the relevance of thepreferred-habitat theory: the U.K. pension reform of 2004 and the U.S. Treasury buyback program of 2000–
01.
9. Kohn (2009) and Yellen (2011) mentioned the preferred-habitat theory as a key mechanism behind the eﬀects
of the Federal Reserve’s large-scale asset purchases on long-term interest rates.
10. Our sample period does not include the period after the expansion of the QQE was announced on October 31,
2014.

47

calculated. To examine the net supply eﬀects, we use two approaches: single-equation
regressions and a term structure model. The former approach can flexibly control various factors that aﬀect long-term interest rates, while the latter is more rigorously related
to the preferred-habitat theory. Both approaches confirm that the net supply eﬀects are
statistically significant, which is consistent with prediction (i) above on the preferredhabitat theory. Moreover, the regression approach implies that the net supply eﬀects
were stronger when the arbitragers’ risk aversion was higher, and this relationship isincorporated in the model approach, consistently with prediction (ii) above.11 However,while the regression approach implies that the net supply eﬀects were stronger in thezero interest rate periods when the arbitragers’ risk aversion was relatively high, thisrelationship was not found using the model approach, because the model estimation
results imply that the eﬀects were weaker in the zero interest rate periods given thearbitragers’ risk aversion. Finally we calculate the net supply eﬀects of the BOJ’s JGB
purchases as part of the QQE from both approaches and compare the results with thoseobtained from a simple event-study analysis.
Our regression approach is closely related to Greenwood and Vayanos (2014), who
examine the eﬀects of the supply and maturity structure of U.S. government debt on
bond yields and returns based on the preferred-habitat theory. Unlike us, however, they
focus on the gross supply of government debt and do not use data on the bonds heldby preferred-habitat investors to construct net supply measures. Kuttner (2006) examines the eﬀects of changes in the Federal Reserve’s holdings of long-term securities
on the holding-period excess returns, and Chadha et al. (2013) examine the eﬀects
of the average maturity of U.S. Treasury bonds held outside the Federal Reserve on
forward long-term yields and the term premium. D’Amico et al. (2012) examine theeﬀects through the scarcity channel and duration channel on several components oflong-term U.S. Treasury yields. Besides these, many regression analyses estimate theeﬀects of government debt or a central bank’s purchases of government debt on longterm interest rates, including Laubach (2009) for U.S. government debt12 and D’Amicoand King (2013) and Meaning and Zhu (2011) for the Federal Reserve’s purchases,13
although they examine the eﬀects through broader channels than those motivated by
the preferred-habitat theory.14 Meanwhile, our term structure model approach is based................................
11. Strohsal (2013) examines the net supply eﬀects under time-varying risk aversion using German daily data andobtains results consistent with prediction (ii) above on the preferred-habitat theory.
12. Following Laubach (2009), Kameda (2014) estimates the eﬀects of government debt and budget deficits on
long-term JGB yields using Japanese data. Ichiue and Shimizu (2012) examine the determinants of long-termbond yields, including fiscal conditions, using panel data for 10 developed countries.
13. To examine the eﬀects of a central bank’s purchases of government bonds on long-term interest rates,
many studies use event-study methodologies: for instance, Gagnon et al. (2011), Krishnamurthy andVissing-Jørgensen (2011), Swanson (2011), Neely (2010), and Cahill et al. (2013). Related studies using
Japanese data include Ueda (2012b) and Lam (2011). Some of these studies use regression analyses as well
as event-study analyses.
14. In this relation, Krishnamurthy and Vissing-Jørgensen (2012) show that when the supply of the U.S. government debt is low, the value that investors assign to the liquidity and safety attributes oﬀered by Treasury bonds
is high, and thus the yield on Treasuries is low relative to the yield on corporate bonds that oﬀer less liquidity
and safety. This implies that the preferred-habitat theory can be applied to not only within government bonds
market but also between government bonds and other bond markets. Meanwhile, Greenwood, Hanson, andStein (2010) show that when the supply of long-term bonds by the government is low, private firms issue alarger fraction of their debt long term given the existence of preferred-habitat investors for long-term bonds.

48 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

on a model extended from Hamilton and Wu (2012a),15 who incorporate preferredhabitat investors into an arbitrage-free term structure model as a discrete-time version
of Vayanos and Vila (2009) and estimate it using U.S. data. Also motivated by thepreferred-habitat theory, Li and Wei (2013) estimate an arbitrage-free term structure
model with U.S. Treasury and mortgage-backed securities supply factors as well as observable yield factors and evaluate the eﬀects of the Federal Reserve’s large-scale asset
purchase programs. While all the papers mentioned above conduct empirical analyses using U.S. data, similar analyses using recent Japanese data including the period
under the QQE are very limited.16 Moreover, similar analyses using data on private
preferred-habitat investors as well as a central bank are limited even in the U.S.17
The remainder of the paper is organized as follows. First, we discuss our JGB
data in Section II. Then, the results from a regression approach and a term structure
model approach are reported in Sections III and IV, respectively. Finally, we show theresults calculated from both approaches as well as a simple event-study analysis forthe net supply eﬀects of the BOJ’s JGB purchases in Section V. Section VI concludes.
Appendix 1 explains the construction of the JGB database discussed in Section II andAppendix 2 describes the term structure model used in Section IV.

II. Data on JGB Outstanding and Yields
In this section, we discuss data on the holders and maturity structures of JGBs andthe term structure of JGB yields. The details of the data construction with regard to
the amount outstanding of JGBs categorized by holder and remaining maturity aredescribed in Appendix 1.
Figure 1 presents the amount outstanding of marketable fixed-rate JGBs18 divided
by nominal GDP from January 1992 to September 2014, which corresponds to themain sample period of our analyses in the following sections.19 The upper panel shows
those with all maturities, and the lower panel shows those with remaining maturities
less than 10 years. Besides the total amounts issued by the government, Figure 1................................
15. The model used in this paper is the same as in Koeda (2015), which extends Hamilton and Wu (2012a) byallowing the coeﬃcients in yield-curve factor dynamics as well as the prices of risk to change at the zero
lower bound regime, using latent factors instead of observable factors, and so on. In this paper, we estimate
the model using Japanese data slightly diﬀerent from Koeda (2015).
16. Iwata and Fueda-Samikawa (2013) extensively examine the eﬀects of the QQE on financial markets, including
the analysis following Chadha et al. (2013). BOJ (2015) assesses the eﬀects of the QQE on Japan’s economic
and financial developments during the two years since the introduction of the policy.
17. Using the U.S. flow of funds data, Carpenter et al. (2014) identify the types of investors that are selling to theFederal Reserve and investigate their portfolio adjustments after these sales, without examining the eﬀects on
interest rates. Saito and Hogen (2014) conduct similar analyses using Japanese data. Using a comprehensive
dataset on the sovereign investor base for 45 advanced and emerging market economies, Jaramillo and Zhang(2013) examine the eﬀects on bond yields of “real money investors,” which include institutional investors aswell as national and foreign central banks.
18. The fixed-rate JGBs cover the majority of the government debt in Japan (around 75 percent of the central
government bonds and 60 percent of the general government gross debt as of 2013). We do not use data on
floating-rate bonds, inflation-linked bonds, financial bills, Treasury bills (T-bills), or any other discount bonds
in our analyses. Also, we exclude directly underwritten bonds and focus on marketable bonds.
19. To avoid an endogeneity problem in our analyses, we use the amount outstanding data mainly in face-value
terms rather than market-value terms.

49

Figure 1 Amount Outstanding of Marketable Fixed-Rate JGBs Held by Each Sector/GDP

Note: Seasonally adjusted data. For details on data sources and the data calculation method, see
Appendix 1.

shows those held by four sectors: the BOJ, insurance companies, pension funds, and“arbitragers.” Throughout the paper, we regard insurance companies and pension funds
as well as the BOJ as “preferred-habitat investors,” because these private investors
clearly prefer to hold long-term bonds to match their long-duration liabilities at leastin our sample period as shown below. Accordingly, we define “arbitragers” as all
JGB holders excluding the BOJ, insurance companies, and pension funds. Specifically,
domestic banks, households, and foreigners are included in the arbitragers. The shareof arbitragers in the total amount outstanding of fixed-rate JGBs has been within therange of 40 to 50 percent since the mid-1990s as shown in Figure 2.

50 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Figure 2 Share of Arbitragers in Marketable Fixed-Rate JGBs

Note: Seasonally adjusted data. For details on data sources and the data calculation method, see
Appendix 1.

As shown in Figure 1, the ratio of the amount outstanding of JGBs held by thearbitragers to GDP increased generally in parallel with the total debt-to-GDP ratio
before the BOJ introduced the QQE in April 2013. However, it started to fall as the
BOJ accelerated the pace of its JGB purchases as part of the QQE.20 This movementin the arbitragers’ debt-to-GDP ratio represents the movement in volume of the net
supply of JGBs, which is defined as the issuance (supply) by the government minus thedemand by the preferred-habitat investors, and it is used as a net supply measure in our
analyses.
Figure 3 shows the maturity structures of JGBs held by the arbitragers, private
preferred-habitat investors (insurance companies and pension funds),21 and the BOJ
from 2004 to the end of our sample period (September 2014). While the arbitragers’
maturity structure has been relatively stable, the maturity structures of the preferredhabitat investors (both private and the BOJ) have changed remarkably. Private
preferred-habitat investors, especially life insurance companies, steadily increased
their holdings of JGBs with maturities over 10 years. They have needed to matchthe duration of assets to the long duration of their liabilities under regulations andaccounting standards that force them to reduce their holdings of risky assets such as................................
20. Before the introduction of the QQE, the BOJ gradually increased its purchase of JGBs as part of its monetaryeasing measures after the global financial crisis. Concurrently, pension funds have decumulated their asset
holdings including JGBs to finance their rising pension payments since around 2008, and this has been an
increasing factor in the arbitragers’ debt-to-GDP ratio (Figure 1) and their share (Figure 2).
21. The “private” preferred-habitat investors actually include Japan Post Insurance (privatized in 2007) and public
pension funds. See Appendix 1 for details.

51

Figure 3 Maturity Structure of JGBs Held by Each Sector

Note: Seasonally adjusted data. For details on data sources and the data calculation method, see
Appendix 1.

stocks.22 The BOJ has increased its holding of JGBs with maturities between 3 years
and 10 years since the implementation of the QQE, while it has reduced the share ofthose with maturities less than 3 years in its JGB portfolio.
The average maturities of JGBs held by each sector as well as the total average................................
22. In addition to the prolonged low profitability of stocks since the bursting of the bubble economy in the 1990s,
mark-to-market accounting (introduced in 2000) and solvency margin regulations (revised in 2012, when therisk coeﬃcient for changes in domestic stock prices was raised from 10 percent to 20 percent) intensified
Japanese life insurers’ stance of reducing risks associated with stockholdings. See, for instance, Severinson
and Yermo (2012) and Kan et al. (2013).

52 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Figure 4 Average Maturities of JGBs Held by Each Sector

Note: Seasonally adjusted data. For details on data sources and the data calculation method, see
Appendix 1.

maturities are shown in Figure 4. Insurance companies have sharply extended their average maturities while reducing the share of medium-term bonds in their JGB portfoliowith maturities less than 10 years (shown in the lower panel). The BOJ has drastically extended its average maturity since the implementation of the QQE, especiallyin its JGB portfolio with maturities less than 10 years.23 As a result, the arbitragers’
average maturities, which had increased since around 2009, leveled oﬀ in their JGB................................
23. After the end of our sample period (not shown in Figure 4), the BOJ further extended its average maturity
as it announced that “the average remaining maturity of the Bank’s JGB purchases will be extended to about
7–10 years” on October 31, 2014 through an expansion of the QQE.

53

Figure 5 Decomposition of the Arbitragers’ Average Maturities

portfolio with all maturities and started to decline in that with maturities less than 10
years. These average maturities of the arbitragers are used as key net supply measuresfor explaining term spreads in our analyses in Section III. In Figure 5, the changes in
the arbitragers’ average maturities since 2008 are decomposed into the changes in the
average maturities of private preferred-habitat investors, the BOJ, and the total issuanceby the government as well as the changes in weights among them. Before 2013, while
the private preferred-habitat investors’ maturity extension had been a decreasing factor
in the arbitragers’ average maturity, the maturity extension of the total issuance oﬀset
and overwhelmed it, which extended the arbitragers’ average maturity as a result. After
2013, the BOJ’s maturity extension was added as another decreasing factor, but it was
oﬀset by the eﬀect of the increase in the BOJ’s share that had a relatively shorter aver-

54 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Figure 6 Zero-Coupon Yields

Note: The zero-coupon yield data are provided by Bloomberg. The shaded area indicates zero lower
bound periods. The graph ends in March 2015.

age maturity than the arbitragers as well as the eﬀect of the maturity extension of thetotal issuance. Meanwhile, the BOJ’s maturity extension overwhelmingly aﬀected thearbitragers’ average maturity in their JGB portfolio with maturities less than 10 years.
Finally, Figure 6 and Figure 7 show the data on JGB yields. Throughout the paper,
we use the zero-coupon yields calculated by Bloomberg. As shown in Figure 6, the1-year and 3-year yields have been very low since the zero interest rate policy was first
implemented in 1999. The 10-year and 20-year yields have steadily declined since themid-2000s, while the pace of decline in the 10-year yield has been faster than in the 20year yield. In Figure 7, it can be clearly seen that the yield curve for relatively shorter
maturities flattened between 2009 and 2013, and then the yield curve for maturities
longer than 6 years flattened after 2013 as a result of the QQE.

III. Regression Approach
In this section, we examine the eﬀects of the net supply of JGBs on the term structure ofinterest rates and the risk premium on long-term bonds using a regression approach. As
the dependent variables representing the term structure, we focus on two measures ofterm spreads: the diﬀerence between zero-coupon yields on 10-year and 3-year JGBs

55

Figure 7 Yield Curves

Note: The zero-coupon yield data are provided by Bloomberg.

and the diﬀerence between the yields on 20-year and 10-year JGBs. The corresponding
net supply measures we mainly use are the average maturity of JGBs with maturities
less than 10 years held by the arbitragers (defined in Section II) and the average maturity of JGBs with all maturities held by the arbitragers, respectively. As the dependent
variables representing the risk premium, we use the 1-year and 3-year holding-period
excess returns of 10-year JGBs. The corresponding net supply measures are the ratioof JGBs with maturities less than 10 years held by the arbitragers to nominal GDP as
well as the average maturity of those JGBs held by the arbitragers. Unless otherwise
mentioned, we use monthly data from January 1992 to September 2014.
Our regression approach is closely related to Greenwood and Vayanos (2014, GV
henceforth). However, besides the diﬀerence between gross and net supply measures
mentioned in Introduction, our choices of dependent variables and net supply measures
diﬀer slightly from GV. They use long-term yields or returns rather than term spreads orexcess returns as dependent variables while using a short-term (1-year) yield as a control variable (or alternatively, they use the spreads between long-term and short-termyields as dependent variables). We do not use the 1-year yield either for term spreads
or as a control variable because it was very low and moved little due to the zero interest rate policy for a significant part of our sample period. Regarding the net supply
measures, we do not use the maturity-weighted debt-to-GDP ratio, which is GV’s main

56 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

supply measure, because its movement was predominantly driven by the strong upward
trend of the debt-to-GDP ratio in Japan. While the maturity-weighted debt-to-GDP ratio can be decomposed into the average maturity and the debt-to-GDP ratio, we use
only the average maturity for the equations of term spreads and both the average maturity and the debt-to-GDP ratio separately for the equations of excess returns. Besides
GV, we follow Laubach (2009) in controlling the economic fundamentals for the term
spreads and Cochrane and Piazzesi (2005) in using their proposed return-forecasting
factor as an explanatory variable for the holding-period excess returns.
There are mainly two econometric issues that need to be addressed in our regression
approach. First, some of our net supply measures and control variables have a unit root,
while the null hypotheses of a unit root are rejected for our dependent variables except
for the 10-year/3-year yield spread. For the 10-year/3-year spread equation, we identify a single cointegrating relationship and estimate it by the fully-modified ordinary
least squares (FM-OLS) method. For the other equations, we report level-regression
results estimated by OLS with t-statistics using Newey and West (1987) standard errors to deal with serially correlated errors. Second, the arbitragers’ average maturities
could be endogenous and aﬀected by (as well as aﬀecting) the term spreads. We calculate average maturities mainly in face-value terms rather than market-value terms
to avoid this endogeneity problem, but the concern still remains even with the facevalue average maturities. In general, a widening of term spreads is likely to induce thegovernment to shift the issuance of its debt toward shorter maturities, while it induces
private preferred-habitat investors to hold government bonds with longer maturities.
Both of these tendencies generate a negative relationship between term spreads and thearbitragers’ average maturities and thus would bias our regression outcomes toward
smaller net supply eﬀects. We address this issue by taking the instrumental variable
estimation approach.
In what follows, we present the estimation specifications and results for the 10year/3-year spread, the 20-year/10-year spread, and the holding-period excess returns,
in turn.
A. Regression of the 10-year/3-year Yield Spread
Our baseline specification of the regression equation of the 10-year/3-year yield spread,, is expressed as follows:y3,10t= β + β x x10y3,10t + β1 z1t + β3 z3t + ut ,t(1)

where x10
t is the average maturity of JGBs with maturities less than 10 years held by
the arbitragers, z1t is the 10-year/3-year spread of nominal GDP trend growth, and z3t
is the equity premium. β, β x , β1 , and β3 are parameters to be estimated and ut is theerror term. Following Laubach (2009), we try to control the expected trend growth
in real consumption, the expected inflation, and the time variation in risk aversion as
fundamental determinants of nominal long-term interest rates.24 Due to unavailability................................
24. In the Ramsey model of optimal growth with a representative household with CES utility, the real rate of
return on capital net of depreciation is determined by the net growth rate of per capita consumption, theintertemporal elasticity of substitution, and households’ rate of time preference. For details, see Laubach

57

Table 1 Unit Root and Cointegration Tests

Note: ∗∗∗ and ∗∗ indicate statistical significance at the 1 percent and 5 percent levels, respectively.

of data on expected long-term trend growth and inflation for our entire sample period,
we use a backward moving average with triangular weights of nominal GDP growth asa proxy for the combination of expected real trend growth and inflation. The spread issimply calculated as the diﬀerence between the 10-year moving average and the 3-year
moving average. For risk aversion, we use an equity premium, which is a measure of
expected excess returns of risky over risk-free assets, as a proxy.25 We do not control
the short-term deviations from the natural rate of interest caused by nominal rigidities
as well as the counter-cyclical monetary policy rule, which would provide little information in addition to the nominal trend-growth spread for the long-term yield spread.
Other candidates for control variables are discussed below.
As summarized in Table 1, according to the Dickey–Fuller test, the null hypothesisof a unit root for all the above dependent and explanatory variables cannot be rejected.
We then conduct Johansen’s cointegration test and confirm the existence of a single
cointegrating relationship in the above set of variables.
Before estimating the identified cointegrating relationship of equation (1), we conduct the first-stage regression of the arbitragers’ average maturity on instrumental variables to deal with the possible endogeneity problem mentioned above. Following GV,
we use the debt-to-GDP ratio, which is driven mainly by the accumulation of past
deficits rather than the current market conditions, as an instrumental variable. Specifically, the one-month lagged ratio of JGBs (less than 10 years) held by the preferred..........................................................................................................................................
(2009).
25. Following Laubach (2009) and Kameda (2014), we use the equity premium based on the dividend yield as aproxy for risk aversion. More specifically, our measure is computed as the ratio of the dividend componentof national income (SNA data) to the sum of the market value of “shares and other equities” (flow of fundsdata) held by households, minus the 10-year JGB yields. For this equity premium as well as GDP, we linearlyinterpolate the original quarterly data to obtain monthly data.

58 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 2 Baseline Regression of 10-year/3-year Yield Spread

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

habitat investors (including the BOJ) to nominal GDP and its square are used here.26
The results of this first-stage regression are summarized in the left part of Table 2. We
also confirm the existence of a single cointegrating relationship in the obtained fitted
values with the other explanatory variables and dependent variable in equation (1).
As the second-stage regression, we estimate the cointegrating relationship of equation (1) by the FM-OLS method to obtain asymptotically unbiased estimates.27 The
results are summarized in the right part of Table 2. The estimated coeﬃcient on thearbitragers’ average maturity is positive and significant at the 5 percent critical level.
This implies that the net supply of relatively longer-term (but less than 10 years) JGBs
tends to widen the 10-year/3-year spread, which is consistent with the preferred-habitat
theory. The nominal trend-growth spread also has a significantly positive relationshipwith the long-term yield spread, which is consistent with neoclassical growth theory.
The coeﬃcient on the equity premium is significantly negative, which implies that anincrease in households’ (final investors’) risk aversion tended to shift their demand
from equities to 10-year JGBs rather than to 3-year JGBs and tighten the 10-year/3year spread in our sample period. Figure 8 shows the decomposition of the fitted values (adjusted by the constant term) into three explanatory variables, from which we
can see that the decrease in the arbitragers’ average maturity together with a shrinking trend-growth spread have contributed to tightening of the 10-year/3-year spread inrecent years.
Table 3 summarizes the results from the specifications using alternative measures of
the net supply of JGBs, while the two control variables are the same as in the baseline
specification. We could not identify a single cointegrating relationship in some ofthese specifications, but we report level-regression results estimated by OLS with t................................
26. We use the preferred-habitat investors’ debt-to-GDP ratio as an instrument because it is more exogenous (interms of the J-statistics) with respect to the term spread and its upward trend is less steep than the total
debt-to-GDP ratio. We have tried many alternative sets of instrumental variables and confirmed that our main
results in our regression approach are generally robust.
27. In the FM-OLS estimation, we estimate the long-run covariance matrices in the cointegrating equation andstochastic regressors innovations using a kernel approach with a Bartlett kernel and Newey–West fixed bandwidth.

59

Figure 8 Decomposition of the 10-year/3-year Yield Spread

Note: The constant term is adjusted. For details on the results of the estimation, see Table 2. The
arbitragers’ average maturity in the above figure is the original (not instrumented) data.

statistics using Newey and West (1987) standard errors in Table 3. The column titled“baseline” shows the OLS estimation result of the baseline specification, in which theestimated coeﬃcients are largely unchanged from the FM-OLS estimation result shownin Table 2. Column (i) shows the result using the original (not instrumented) data of
the arbitragers’ average maturity. The estimated coeﬃcient on the average maturity isinsignificant and smaller than that in the baseline result, reflecting the downward bias
due to the endogeneity problem mentioned above.28 In column (ii), the change in theratio of JGBs (less than 10 years) held by the arbitragers to nominal GDP, smoothedby the Hodrick–Prescott filter, is included as an additional net supply measure that
captures the movements in volume of the net supply. The estimated coeﬃcient on thismeasure is positive but insignificant, while the signs and significance of the average
maturity and control variables are maintained. In column (iii), we use the share of
JGBs with maturities in excess of 3 years held by the arbitragers in their JGBs withmaturities less than 10 years (the share of maturities of 3 to 10 years within those lessthan 10 years) as an alternative net supply measure.29 The estimated coeﬃcient on thismeasure is positive but insignificant.
................................
28. The estimated coeﬃcient on the original average maturity is significant when we use the usual (not Newey–West) standard error (the t-statistic is 2.24). Meanwhile, the same coeﬃcient estimated by FM-OLS is evensmaller (0.08) and insignificant.
29. Modigliani and Sutch (1967) point out that the average maturity fails to distinguish changes occurring at the
short end of the maturity range from those at the long end. They use in their analysis the proportion of the total
volume of outstanding debt accounted for by issues falling within a specified maturity range as an alternative
measure of maturity composition.

60 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 3 Regression of 10-year/3-year Yield Spread (Alternative 1)

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

Column (iv) shows the result using the average maturities of JGBs with maturities
less than 10 years held by the BOJ and those issued by the government minus the holdings of private preferred-habitat investors separately (the latter equals the holdings ofthe arbitragers and the BOJ). The estimated coeﬃcient on the BOJ’s average maturity
is significantly negative, which is consistent with the preferred-habitat theory. The absolute value of the estimated coeﬃcient can be regarded as relatively large comparedwith the estimated coeﬃcient on the other component of the net supply, consideringthat the BOJ’s share in JGBs with maturities less than 10 years has been around 15
percent on average since the data became available in 2001 (while the share of thearbitragers plus the BOJ has been around 65 percent). This result may imply someheterogeneity between the BOJ and other (private) preferred-habitat investors and may
also reflect the downward bias caused by the endogenous interaction between the term
spread and the average maturities of the government and private preferred-habitat investors as mentioned above.30 In Section V, we calculate the eﬀect of the BOJ’s JGB
purchases and maturity extension as part of the QQE based on this result as well as thebaseline result and other approaches.
Table 4 summarizes the results using alternative sets of control variables, while thenet supply measure is the same as in the baseline specification. Column (v) shows theresult using the real trend-growth spread (based on real GDP) and the trend-inflation
spread (based on the consumer price index) instead of the nominal trend-growth spread.
For both variables, backward moving averages with triangular weights are used and the................................
30. Kuttner (2006) shows that the eﬀect of changes in the Federal Reserve’s holdings of long-term securities had alarger and statistically significant eﬀect on the holding-period excess returns than those in the composition ofprivately held debt because the latter includes the potentially endogenous issuance of new Treasury securities.

61

Table 4 Regression of 10-year/3-year Yield Spread (Alternative 2)

Note: Sample period: 1992M02-2014M09. ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent,
5 percent, and 10 percent levels, respectively. Newey–West adjusted t-statistics are presented
in the brackets.

spread is calculated as the diﬀerence between the 10-year moving average and the 3year moving average. The estimated coeﬃcients on both variables are significantly
positive, while the adjusted R-squared is slightly lower than in the baseline regression.
In columns (vi) and (vii), the volatility of the 10-year/3-year JGB zero-coupon yieldspread (dependent variable) and the corresponding spread of the U.S. Treasury Bonds
are included, respectively, as an additional control variable. However, the estimatedcoeﬃcients on these additional variables are insignificant with wrong signs.
Finally in Table 5, we show the results of sub-sample regressions using the baseline specification. In column (viii), the sample period is limited to the three sub-periods
under the zero lower bound of the short-term nominal interest rate: from March 1999
to July 2000, from March 2001 to June 2006, and from December 2008 to September
2014 (the end of the sample period), which correspond to the “zero lower bound (ZLB)
regime” in the term structure model in Section IV. In column (ix), the sample period isfurther limited to the last sub-period after December 2008. In both results, especiallyin column (ix), the estimated coeﬃcients on the arbitragers’ average maturity are larger
than that in the baseline full-sample regression, which imply that the net supply eﬀect
on the 10-year/3-year spread was stronger in the zero lower bound periods including
the recent period after the global financial crisis. A possible interpretation based on thepreferred-habitat theory is that the arbitragers’ increasing aversion to the duration risks
strengthened the net supply eﬀect through the deepened market segmentation in thezero lower bound periods. To consider the possibility of the time-varying eﬀect of the
net supply depending on the risk aversion, we estimate another specification in which
the arbitragers’ average maturity in the baseline specification is replaced with the product of the average maturity and the equity premium. The latter in the product is used as
an independent variable representing the risk aversion and was generally higher in the

62 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 5 Regression of 10-year/3-year Yield Spread (Alternative 3)

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

zero lower bound periods. According to the result shown in column (x), the estimatedcoeﬃcient on this risk-weighted net supply measure is positive and significant, while
the signs and significance of other explanatory variables are maintained. This result
together with the baseline result implies that the net supply eﬀect on the 10-year/3year spread was stronger when the risk aversion was higher, which supports the above
conjecture based on the preferred-habitat theory.
B. Regression of the 20-year/10-year Yield Spread
Our baseline specification of the regression equation of the 20-year/10-year yield, corresponds with that of the 10-year/3-year spread equation, and isspread, y10,20t
expressed as follows:= β + β x xt + β2 z2t + β3 z3t + ut ,y10,20t(2)where xt is the average maturity of JGBs (with all maturities) held by arbitragers,31 z2t
is the 20-year/10-year spread of nominal GDP trend growth, and z3t is the equity premium. As summarized in the left part of Table 1, according to the Dickey–Fuller test,
the null hypothesis of a unit root for the dependent variable is strongly rejected at the
1 percent critical level, while those for all explanatory variables cannot be rejected.32
Accordingly, we report level-regression results estimated by OLS with t-statistics using
Newey and West (1987) standard errors.
As in the case of the 10-year/3-year spread equations, we conduct two-stage leastsquare regression to deal with the possible endogeneity problem. In the first-stage
regression, the arbitragers’ average maturity is regressed on the one-month lagged................................
31. We use the arbitragers’ average maturity of JGBs with all maturities rather than those over 10 years because
the issuance of JGBs with maturities over 10 years was very limited in the early part of our sample period(especially before 1998).
32. According to Johansen’s cointegration test, we can identify a single cointegrating relationship in the three
explanatory variables in equation (2).

63

Table 6 Baseline Regression of 20-year/10-year Yield Spread

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

preferred-habitat investors’ debt-to-GDP ratio, its square, and the share of JGBs withmaturities over 10 years in the total issuance, as summarized in the left part of Table 6.
In the second-stage regression, we estimate equation (2) using the fitted values of thefirst-stage regression. The results are summarized in the right part of Table 6. The estimated coeﬃcient on the arbitragers’ average maturity is positive and significant at the 1
percent critical level, which implies that the net supply of relatively longer-term JGBs
tends to widen the 20-year/10-year spread as well as the 10-year/3-year spread, whichis consistent with the preferred-habitat theory. The nominal trend-growth spread also
has a significantly positive relationship with the super-long-term yield spread, consistently with neoclassical growth theory. The coeﬃcient on the equity premium issignificantly positive rather than negative, in contrast to the result for the 10-year/3year spread. It may be naturally understood that an increase in investors’ risk aversion
tends to widen the 20-year/10-year spread because they become averse to the duration
risk for this super-long-term spread. In our sample period, the increasingly risk-averse
investors tended to shift their demand from equities to 10-year JGBs rather than to
20-year JGBs or 3-year JGBs. Figure 9 shows the decomposition of the fitted values(adjusted by the constant term) into three explanatory variables, from which we can seethat the increase in the arbitragers’ average maturity has contributed to the widening of
the 20-year/10-year spread since around the recent financial crisis.
Table 7 summarizes the results from the specifications using alternative measuresof the net supply of JGBs, while the two control variables are the same as in the baseline specification. The column titled “baseline” shows exactly the same result as in
Table 6. Column (i) shows the result using the original (not instrumented) data of
the arbitragers’ average maturity. The estimated coeﬃcient on the average maturity isslightly smaller than that obtained from the instrumental variable estimation, although
the diﬀerence is much smaller than in the case of the 10-year/3-year spread equations.
In column (ii), the change in the ratio of JGBs held by the arbitragers to nominal GDP,smoothed by the Hodrick–Prescott filter, is included as an additional net supply measure. The estimated coeﬃcients on this measure as well as the average maturity of the
net supply are both significantly positive. In column (iii), we use the share of JGBs
with maturities in excess of 10 years held by the arbitragers in their total holdings of

64 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Figure 9 Decomposition of the 20-year/10-year Yield Spread

Note: The constant term is adjusted. For details on the results of the estimation, see Table 6. The
arbitragers’ average maturity in the above figure is the original (not instrumented) data.

JGBs as an alternative net supply measure. The estimated coeﬃcient on this measure
is positive and significant at the 1 percent critical level.
Column (iv) shows the result using the average maturities of JGBs held by the BOJ,
those held by private preferred-habitat investors, and those issued by the government,
separately. The estimated coeﬃcients on the average maturities of the BOJ and private preferred-habitat investors are significantly negative, which are consistent withthe preferred-habitat theory. The magnitudes of these estimated coeﬃcients generally
correspond to their shares in the total outstanding of JGBs. (The BOJ’s share has beenaround 15 percent on average since the data became available in 2001, while the private preferred-habitat investors’ share has been around 40 percent.) On the one hand,
there may be some downward bias caused by the endogeneity problem in the estimatedcoeﬃcient on the private preferred-habitat investors’ average maturity. On the other
hand, since the BOJ’s average maturity has been far below 10 years, its eﬀect on the
20-year/10-year spread may be limited compared with the private preferred-habitat investors’ average maturity that has increased to well over 10 years as shown in Figure 4
in Section II.
Table 8 summarizes the results using alternative sets of control variables, while thenet supply measure is the same as in the baseline specification. Column (v) shows
the result using the real trend-growth spread and the trend-inflation spread instead of
the nominal trend growth spread. The estimated coeﬃcients on the real trend-growth
spread is significantly positive, while that on the trend-inflation spread is insignificant.
In columns (vi) and (vii), the volatility of the 20-year/10-year JGB yield spread (depen-65

Table 7 Regression of 20-year/10-year Yield Spread (Alternative 1)

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

dent variable) and the corresponding spread of the U.S. Treasury Bonds are included,
respectively, as an additional control variable. While the estimated coeﬃcient on theformer is insignificant, that on the latter is strongly significant and positive, in contrast
to the result for the 10-year/3-year spread, and greatly improves the adjusted R-squared
from the baseline result.
Finally in Table 9, we show the results of sub-sample regressions using the baseline
specification. As in the results for the 10-year/3-year spread, column (viii) shows theresult when the sample period is limited to the three sub-periods under the zero lower
bound of the short-term nominal interest rate, and column (ix) shows the result when
the sample period is further limited to the last sub-period after December 2008. In bothresults, the estimated coeﬃcients on the arbitragers’ average maturity are smaller thanthat in the full sample period, in contrast to the results for the 10-year/3-year spread.
Meanwhile, column (x) shows that the estimated coeﬃcient on the risk-weighted net
supply measure, the product of the arbitragers’ average maturity and the equity premium, is significantly positive, as in the result for the 10-year/3-year spread. The latter
result implies that the net supply eﬀect on the 20-year/10-year spread was stronger
when the arbitragers’ risk aversion was higher, while the former implies that the eﬀect
was not stronger in the zero lower bound periods when the risk aversion represented by
the equity premium was higher. One possible factor that could reconcile these seemingly conflicting results is the share of JGBs held by the arbitragers in the total amountoutstanding, which declined in the early 1990s and then dropped again after the recent financial crisis (especially their share in JGBs with maturities over 10 years) as
shown in Figure 2 in Section II. When the presence of the arbitragers is small, the net

66 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 8 Regression of 20-year/10-year Yield Spread (Alternative 2)

Note: Sample period: 1992M02-2014M09. ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent,
5 percent, and 10 percent levels, respectively. Newey–West adjusted t-statistics are presented
in the brackets.

Table 9 Regression of 20-year/10-year Yield Spread (Alternative 3)

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets.

supply eﬀect would not change significantly in response to changes in the arbitragers’
risk aversion. Another possibility is that long-term (as well as short-term) interest rates
become less responsive to any factors, including the net supply shocks, when the shortterm interest rate is constrained by the zero lower bound. We check this possibility in
Section IV using a term structure model that explicitly considers the zero lower boundregime as well as the normal regime.

67

C. Regression of Holding-Period Excess Returns
Next, we present the estimation specifications and results for the holding-period excess
returns. Our specifications of the 1-year and 3-year holding excess returns of 10-year
10
JGBs, rx10
t+1,12 and rxt+1,36 , respectively, are expressed as follows:
10
9
1
rx10
t+1,12 ≡ (10 × yt − 9 × yt+12 ) − yt10
= β01 + β x x10
t + β xx xxt + β4 z4t + u1t ,(3)

7(10 × y10t − 7 × yt+36 )
− y3t
3
10
= β03 + β x x10
t + β xx xxt + β4 z4t + u3t ,

(4)

rx10
t+1,36 ≡where ynt is the yield on n-year JGBs in period (month) t, x10
t is the average maturity of JGBs with maturities less than 10 years held by the arbitragers, xx10
t is theratio of those JGBs held by the arbitragers to nominal GDP, and z4t is the returnforecasting factor proposed by Cochrane and Piazzesi (2005).33 We use xx10
t as well
asnet
supplymeasurestocapturethevolume
as
well
as
the
maturity
strucas x10tture of the net supply. As mentioned in the beginning of this section, the product ofthese two measures corresponds to the maturity-weighted debt-to-GDP ratio, which is
the main supply measure used by GV. Regarding the return-forecasting factor, it is con
structed from the fitted value of a regression of (1/4) 5n=2 rxnt+1,12 on a constant and the1- through 5-year forward rates. As we use the realized (ex-post) holding-period excess
returns as dependent variables, the end of the sample period is September 2013 for the
1-year holding excess return equation (3), and is September 2011 for that of the 3-year
holding excess return equation (4).
As summarized in the left part of Table 1, according to the Dickey–Fuller test, thenull hypotheses of a unit root for the dependent variables are rejected at the 5 percent
critical level, while those for all explanatory variables cannot be rejected.34 Accordingly, we report level-regression results estimated by OLS with t-statistics using Newey
and West (1987) standard errors. The results are summarized in Table 10. Regarding
the 1-year holding excess return, the estimated coeﬃcients on the arbitragers’ average
maturity and their debt-to-GDP ratio are both positive but only the latter coeﬃcient
is significant, which implies that a larger volume of the net supply of JGBs tends toincrease the risk premium on the 10-year bond. When the sample period is limited tothe three sub-periods under the zero lower bound of the short-term nominal interest
rate, as shown in column (ii), the estimated coeﬃcients on the two net supply measures
are larger than those in the full sample period, although the coeﬃcient on the average
maturity is still insignificant. Regarding the 3-year holding excess return, as shown incolumn (v), the estimated coeﬃcients on the two net supply measures are both positiveand significant at the 1 percent critical level, which implies that a relatively longer-term................................
33. Kuttner (2006) uses Cochrane and Piazzesi’s (2005) return-forecasting factor as a control variable in his
regression of the holding-period excess returns on the maturity structure of the Federal Reserve’s holding
securities.
34. According to Johansen’s cointegration test, we can identify a single cointegrating relationship in the three
explanatory variables in equations (3) and (4).

68 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 10 Regression of Holding-Period Excess Returns

Note: ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10 percent levels,
respectively. Newey–West adjusted t-statistics are presented in the brackets. The wealth measure is defined as the product of the 1-year (or 3-year) lag of the arbitragers’ maturity-weighted
debt-to-GDP ratio (the product of the two net supply measures) and the 1-year (or 3-year) holding
excess return.

and a larger volume of the net supply of JGBs tends to increase the risk premium on
the 10-year bond. When the sample period is limited to the three sub-periods under
the zero lower bound, as shown in column (vi), the estimated coeﬃcients on the two
net supply measures are larger than those in the full sample period, while the signs andsignificance are maintained. This implies that the net supply eﬀect on the risk premium
was larger in the zero lower bound periods.
We then consider the possibility of the time-varying eﬀect of the net supply depending on the arbitragers’ risk aversion by estimating two alternative specifications.
First, as in the analysis of term spreads, the two net supply measures are replaced withthe product of the two measures and also the equity premium. As shown in columns(iii) and (vii) for the 1-year and 3-year holding excess returns, respectively, the estimated coeﬃcients on these risk-weighted net supply measures are both positive but
insignificant. Second, following GV, the product of the two net supply measures andthe measure of the change in the arbitragers’ wealth during the holding periods is included as an explanatory variable, in addition to the two net supply measures. The
wealth measure is defined as the product of the 1-year (or 3-year) lag of the arbitragers’
maturity-weighted debt-to-GDP ratio (the product of the two net supply measures) andthe 1-year (or 3-year) holding excess return. As shown in columns (iv) and (viii) for
the 1-year and 3-year holding excess returns, respectively, the estimated coeﬃcients onthese wealth measures are both negative, although only the coeﬃcient in the 1-year return equation is significant. This implies that the net supply eﬀects on the risk premium
are stronger when the arbitragers have lost their wealth and thus their risk aversion ishigher.
Throughout this section, from our regression approach, we can conclude that the net
supply eﬀects on the term structure of interest rates and the risk premium on long-termbonds are statistically significant in most alternative specifications, which is consistent69

with the preferred-habitat theory. Moreover, many regression results imply that theeﬀects are stronger when the short-term interest rate is constrained by the zero lower
bound and the arbitragers’ risk aversion is higher.

IV. Term Structure Model Approach
In this section, we report the results from a term structure model that incorporates
preferred-habitat investors.35 In the model, yields for all maturities are expressed asaﬃne functions of three yield-curve factors. Moreover, we consider the zero lower
bound (ZLB) regime as well as the normal regime, allowing the coeﬃcients on theyield-curve factor dynamics and the prices of risk to diﬀer between the two regimes.
Using this model, we examine the eﬀects of the model-implied net supply measures of
JGBs on term spreads and holding-period excess returns as in our regression approachin Section III. We also use this model in Section V to derive the term premium andexamine the eﬀects of the BOJ’s JGB purchases and maturity extension.
Here we just give a brief outline of the model of the normal regime. Details of themodel including the ZLB regime are described in Appendix 2 and Koeda (2015).
There are two types of investors in the JGB market: arbitragers and preferredhabitat investors. The arbitragers choose a fraction, znt , of their JGB portfolio in eachmaturity n (from 1 to N) to maximize the mean-variance expected returns on the portfolio, as follows:max

z1t ,··· ,zNt

E(rt,t+1 |f t ) −γVar(rt,t+1 |f t ) ,2

N
where rt,t+1 = Σn=1
znt rn,t,t+1 is the arbitragers’ rate of return from period t to period t +1
on their JGB portfolio and f t is a 3 ×1 vector of yield-curve factors assumed to follow a
VAR (1) process: f t+1 = c + Φf t + Σut+1 . The parameter γ captures the arbitragers’ risk
aversion. In the ZLB regime, arbitragers explicitly consider the possibility of a regime
shift to the normal regime in their optimization problem, as described in Appendix 2.
On the other hand, the preferred-habitat investors demand JGBs with a particularmaturity depending solely on the corresponding yield on that particular maturity: they
demand more of the bonds when the yield on that maturity increases. Meanwhile, thegovernment would also decide to issue its bonds with a maturity depending on the yieldon that particular maturity: it issues fewer of the bonds when the yield on that maturity
increases. Therefore, the net supply of the JGBs with maturity n, the issuance by thegovernment minus preferred-habitat investors’ demand, can be expressed as:

xnt = ςt,n − αn yt,n ,for each n, where xnt is the net supply of the JGBs with maturity n divided by the arbitragers’ net wealth, ςt,n is an aﬃne function of f t , and the parameter αn represents
the sensitivity to the n-period log yield, yt,n . Then, in the market equilibrium where................................
35. The model used in this paper is the same as in Koeda (2015), which is an extension of Hamilton and Wu(2012a). The model of the normal regime described in the text is the same as in Hamilton and Wu (2012a).

70 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

znt = xnt for all n, the n-period log bond prices, pt,n , and log yields, yt,n , can be expressed as an aﬃne function of f t as:
pt,n = −n yt,n = ān + b̄n f t ,for all n, given that the risk-free one-period rate, yt,1 , is assumed to follow an aﬃnefunction of f t .
From this model, we can derive the term spread between j- and k-period yields( j > k), yt, j − yt,k , and the expected k-period holding excess return of j-period bonds,j
E t (rxt+1,k), as follows:yt, j − yt,k = c̃ j,k + Γ̃ j,k f t
⎫
⎧
N
⎪
⎪
⎪
⎪


⎬
⎨ b̄ j−1 b̄k−1,+γ ⎪znt b̄n−1 ⎪
−
ΣΣ
⎪
⎪
⎭
⎩ j
k


n=2
N

j
E t (rxt+1,k) = c j,k + Φ j,k f t + γb̄ j−1 ΣΣznt b̄n−1 ,

(5)
(6)

n=2

where c̃ j,k , Γ̃ j,k , c j,k , and Φ j,k are combinations of parameters in the model. The point
here is that znt (= xnt ) is included in the third term on the right-hand side of equations(5) and (6).36 We regard this term as the model-implied net supply measure in eachequation.
We estimate the model using monthly data of the zero coupon yield (the same as
in Section III) on 3-month, 3-year, 5-year, and 10-year JGBs. As in Koeda (2015),
we apply Hamilton and Wu (2012b) minimum chi-squared estimation to estimate theterm structure model coeﬃcients.37 Meanwhile, some deep parameters including γ
representing the risk aversion are not estimated in the model. In this paper, we try
to estimate γ in equations (5) and (6) by OLS, using the actual data of term spreads
and ex-post holding-period excess returns as dependent variables, respectively.38 We
construct the model-implied net supply measures as explanatory variables for the above
regressions, by plugging in the data on JGB’s maturity structure described in Section
II for znt in the third term on the right-hand side of equations (5) and (6). In these
regressions, the sample period is from January 1992 to September 2014, as in the
regression analysis in Section III. We distinguish between the normal and ZLB regimes,
the latter of which consists of three sub-periods: from March 1999 to July 2000, fromMarch 2001 to June 2006, and from December 2008 to September 2014,39 by using
dummy variables.
In what follows, we first check the model-implied relationship between the maturity structure (znt ) and the net supply measures in term spreads and holding-period................................
36. As described in Appendix 2, the price of risk can be expressed as a function of zt in this model.
37. We first estimate the term structure model coeﬃcients under the normal regime using the data from February
1992 to February 1999 and then, given the normal-regime parameters, the term structure model coeﬃcients
under the ZLB regime are estimated using the data from December 2008 to September 2014.
38. In these regressions, we relax the model assumption by allowing the net supply of the JGBs to depend on not
only bond yields but also other possible exogenous shocks.
39. The identification of the ZLB regime is based on Hayashi and Koeda (2014).

71excess returns, based on Koeda (2015). Then given these net supply measures and theestimated yield-curve factors, we try to estimate γ in equations (5) and (6), and discuss
the results including the size, significance, and diﬀerence between the normal and ZLB
regimes.
A. Regression of the 10-year/3-year Yield Spread
First we examine the eﬀects of the model-implied net supply measure on the 10-year/3year spread. The net supply measure, the third term on the right-hand side of equation (5), increases when the average maturity of JGBs held by the arbitragers is extended. We check how the change in the maturity structure less than 10 years (znt forn ≤ 10) is related to the net supply measure, using the data on JGB’s maturity structure
described in Section II for znt . Suppose a shock causes the arbitragers to extend theirmaturity by buying 10-year bonds and selling 1-year bonds by a 1 percent share of theirholding JGBs with maturities less than 10 years (at the same time, the preferred-habitat
investors shorten their maturity by selling 10-year bonds and buying 1-year bonds) under the normal regime. Then, the net supply measure widens the 10-year/3-year yieldspread by about 0.23 basis point, given the estimated term structure model coeﬃcientsand assuming the parameter value of the arbitragers’ risk aversion to be γ = 100.40 If,
on the other hand, the arbitragers shorten their maturity (the preferred-habitat investors
extend their maturity) by carrying out the opposite transaction under the ZLB regime,
the net supply measure tightens the 10-year/3-year yield spread by about 0.06 basis
point. Note that these figures in terms of the 10-year/3-year yield spread are very small
because we focus here on the eﬀect of the net supply measure (the third term in equation (5)) and do not take account of the changes in the yield-curve factors (the secondterm).41 The asymmetry between the two regimes reflects the model estimation results
in which the yield-curve factors are more volatile and yields are more responsive to theyield-curve factors under the normal regime, as in Koeda (2015). Therefore, according
to this model, the net supply eﬀect on the 10-year/3-year spread is stronger under thenormal regime than under the ZLB regime, unless the degree of the arbitragers’ risk
aversion changes significantly between the two regimes.
Then, given the model-implied net supply measure and yield-curve factors, weestimate γ in equation (5) by OLS. We also estimate the coeﬃcients on the yieldcurve factors under the two alternative assumptions: they are identical or diﬀerent
between the two regimes.42 As summarized in Table 11, in both specifications withand without the coeﬃcient dummies for the ZLB regime on the yield-curve factors, theestimated coeﬃcient on the net supply measure, γ, is significantly positive. Since γ
represents the arbitragers’ risk aversion in this model, this result implies not only thatthe net supply eﬀect is significantly positive but also that the eﬀect is stronger when
the arbitragers’ risk aversion is higher. However, the size of the estimated γ, diﬀers
substantially between the two specifications. Table 11 also shows the result when the................................
40. Hamilton and Wu (2012a) calibrate this parameter to 100 based on their estimation results using U.S. data.
41. When we calculate the eﬀects of the BOJ’s JGB purchases and maturity extension in Section V, we takeaccount of the changes in the yield-curve factor as well as the net supply measure.
42. The coeﬃcients Γ̃ j,k in equation (5) are estimated in the term structure model and diﬀer between the two
regimes. However, we do not use these estimated coeﬃcients but re-estimate them in the single-equation
regression to improve the fit of the regression.

72 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 11 Regression of 10-year/3-year Yield Spread from the Term Structure Model
Approach

Note: The model-implied net supply measure and the yield-curve factors are estimated from the term
structure model. ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10
percent levels, respectively. t-statistics are presented in the brackets.

sample period is limited to the three sub-periods under the ZLB regime, in column(iii). The estimated coeﬃcient on the net supply measure is positive but insignificant at
the 10 percent critical level. In sum, the net supply of relatively longer-term (but lessthan 10 years) JGBs tends to widen the 10-year/3-year spread, which is consistent withthe preferred-habitat theory. However, the result of the above sub-sample regression as
well as the calculated asymmetry in the model-implied net supply measure between thetwo regimes imply that the net supply eﬀect was not stronger in the zero lower boundperiods, in contrast to the regression analysis in Section III.43
B. Regression of the 20-year/10-year Yield Spread
Next, we examine the eﬀects of the model-implied net supply measure on the 20year/10-year spread. As before, we first check how the change in the maturity structure(znt for all n) is related to the net supply measure in the 20-year/10-year spread equation(5), using the data on JGB’s maturity structure described in Section II for znt . If thearbitragers extend their maturity by buying 20-year bonds and selling 1-year bonds by
a 1 percent share of their total JGB holdings (at the same time, the preferred-habitat
investors shorten their maturity by selling 20-year bonds and buying 1-year bonds) under the normal regime, the net supply measure widens the 20-year/10-year yield spread................................
43. To address the possible endogeneity problem mentioned in Section III, we also conduct two-stage least squareestimation using the same instrumental variables as in Section III or the lags of the model-implied net supply
measure. The results are generally unchanged from those using the original (not instrumented) model-implied
net supply measure shown in Table 11.

73

Table 12 Regression of 20-year/10-year Yield Spread from the Term Structure Model
Approach

Note: The model-implied net supply measure and the yield-curve factors are estimated from the term
structure model. ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10
percent levels, respectively. t-statistics are presented in the brackets.

by about 0.44 basis point, given the estimated term structure model coeﬃcients and assuming the parameter value of the arbitragers’ risk aversion to be γ = 100. If, on theother hand, the arbitragers shorten their maturity (the preferred-habitat investors extend their maturity) by carrying out the opposite transaction under the ZLB regime, thenet supply measure tightens the 20-year/10-year yield spread by about 0.22 basis point.
Although the asymmetry between the two regimes is smaller than in the 10-year/3-year
spread, the net supply eﬀect on the 20-year/10-year spread is again stronger under thenormal regime than under the ZLB regime, given the degree of the arbitragers’ risk
aversion.
Then, given the model-implied net supply measure and yield-curve factors, weestimate equation (5) by OLS. As summarized in Table 12, in both specifications withand without the coeﬃcient dummies for the ZLB regime on the yield-curve factors, theestimated coeﬃcient on the net supply measure, γ, is significantly positive. However,the size of the estimated γ, in both specifications, diﬀers substantially from the results
obtained from the 10-year/3-year spread equation. When the sample period is limited
to the three sub-periods under the ZLB regime, the estimated γ is significantly positiveand its size is slightly larger than those obtained from both the specifications in the fullsample period. In sum, the net supply of relatively longer-term JGBs tends to widen
the 20-year/10-year spread, which is again consistent with the preferred-habitat theory.
However, the result of the above sub-sample regression combined with the calculated
asymmetry in the model-implied net supply measure between the two regimes imply

74 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 13 Regression of Holding-Period Excess Returns from the Term Structure
Model Approach

Note: The model-implied net supply measure and the yield-curve factors are estimated from the term
structure model. ∗∗∗ , ∗∗ , and ∗ indicate statistical significance at the 1 percent, 5 percent, and 10
percent levels, respectively. t-statistics are presented in the brackets.

that the net supply eﬀect in the zero lower bound periods was not necessarily stronger
than that in the full sample period.
C. Regression of Holding-Period Excess Returns
We then examine the eﬀects of the model-implied net supply measure on the holdingperiod excess returns, the third term on the right-hand side of equation (6). As shownin the analysis of the one-period holding excess return in Koeda (2015), the net supply measure increases when the average maturity of JGBs held by the arbitragers is
extended, but there is asymmetry in this relationship between the two regimes: the net
supply measure is more sensitive to the arbitragers’ average maturity under the normal
regime than under the ZLB regime.
Keeping this relationship in mind, given the model-implied net supply measuresand yield-curve factors, we estimate equation (6) using the actual data on the ex-post
1-year and 3-year holding excess returns of 10-year JGBs by OLS. The results are
summarized in Table 13. Regarding the 1-year holding excess return, the estimatedcoeﬃcient on the net supply measure, γ, is significantly positive only in the specifications without the coeﬃcient dummies for the ZLB regime on the yield-curve factors.
Even in this specification, the size of the estimated γ diﬀers substantially from the results obtained from the term spread equations as well as the other specification of theholding-period excess returns. When the sample period is limited to the three subperiods under the ZLB regime, the estimated γ is positive but insignificant. Results
similar to these are also obtained for the 3-year holding excess return. Therefore, we
could not obtain a robust and reliable estimate of γ to examine the net supply eﬀects

75

on the holding-period excess returns from this term structure model approach.44

V. Effects of the BOJ’s JGB Purchases
Based on the analyses in Sections III and IV, we can extract the eﬀects of the BOJ’spurchases of JGBs and maturity extension as part of the QQE, which started in April
2013, on term spreads.45 The idea is simple: we just plug in the contributions of the
BOJ’s JGB purchases and/or maturity extension to the various net supply measures in
the regression equations in the preceding two sections, and calculate the cumulative net
supply eﬀects through our sample period after the implementation of QQE based on
the estimated coeﬃcients. We briefly summarize and compare these calculation resultsin the latter part of this section.
In general, however, it is diﬃcult to identify the eﬀects of a central bank’s bondpurchases on long-term interest rates in the data. As mentioned in Introduction, there
are various channels of transmission of the eﬀects including those that are not captured by our analyses based on the preferred-habitat theory. Moreover, the timing andpersistence of the eﬀects are hard to identify. As shown in Figure 6 in Section II,
long-term interest rates actually started to decline before the QQE was implemented.
This was probably because market participants had widely anticipated since the Prime
Minister Abe took oﬃce near the end of December 2012 that he would appoint a new
BOJ governor who would take a more aggressive monetary easing policy, including
the BOJ’s purchases of more and longer-term JGBs, compared with the governor at thetime whose term was going to expire in April 2013.46 These “anticipated” net supply
eﬀects are not captured, at least directly, in our analyses. Regarding the persistence ofthe net supply eﬀects, it should be distinguished between the instantaneous responseof bond prices to a central bank’s ongoing purchase operations (the “flow eﬀects”) andpersistent changes in bond prices resulting from movements along the bond demand
curve (the “stock eﬀects”), as investigated by D’Amico and King (2013). While ouranalyses using monthly data in the preceding sections focus mainly on the stock effects, the flow eﬀects may also be important, as they could reflect some impairments inliquidity and functioning of the government bond markets as well as updates of market
participants’ expectations about the details of the central bank’s operations.
In what follows, before showing the results calculated from our analyses in thepreceding sections, we conduct a simple event-study analysis of the BOJ’s outrightpurchases of JGBs using daily data, as a reference for comparison. While many eventstudy analyses in the literature focus on a number of oﬃcial announcements regarding
the framework of asset purchase programs that aﬀect market participants’ expectations
about the net supply of the government bonds, we cannot do so for this analysis of the
QQE because there was no major change in the framework of JGB purchase programin the QQE after the initial announcement on April 4, 2013 until the end of our sample
period. Instead, we include each oﬀer date of market operations by the BOJ in our................................

44. Due to this diﬃculty in estimating γ, Koeda (2015) reports her results with some alternative values of γ.
45. We do not calculate the eﬀects of the BOJ’s JGB purchases on holding-period excess returns because the datanear the end of our sample period (1 year or 3 years) are not available.
46. The anticipations of market participants in this period are discussed in, for instance, Ito (2014).

76 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

event set. Therefore, our event-study analysis below may mainly capture the flow
eﬀects rather than the announcement eﬀects of the BOJ’s JGB purchases.
A. Event-Study Analysis
As mentioned above, our baseline event set includes all dates of oﬀer of the BOJ’s
outright purchases of JGBs during the period between April 4, 2013 and September 30,
2014, which amounts to 173 events.47 We also use an alternative event set that focuseson the outright purchases of JGBs with maturities over 10 years, which amounts to 87
events. As long-term interest rates started to decline before the QQE was implemented
as mentioned above, we also examine an extended period from January 4, 2013 to
September 30, 2014, in which the baseline events and alternative events increase to
185 and 90, respectively.48
Regarding the response window, we use one-day and two-day windows around theoﬀer date: the former is measured from the closing level of the working day prior tothe oﬀer date to the closing level of the oﬀer date, and the latter is measured from theclosing level of the two working days prior to the oﬀer date to the closing level of theoﬀer date. We use the two-day window because many market participants anticipate
the details (purchase amount, JGB maturity, etc.) of the operation to some extent in theworking day prior to the oﬀer date. At the same time, however, setting a wider window
increases the risk of including eﬀects on long-term interest rates that are unrelated to
the BOJ’s purchases. We calculate the cumulative changes in long-term interest rates
during the response window of each event as a measure of the eﬀects of the BOJ’s JGB
purchases. Specifically, we examine the eﬀects on the 10-year yield, 20-year yield, 10year/3-year spread, and 20-year/10-year spread on JGBs, which are all the zero-coupon
yields as in the analyses in the preceding sections.
The results are summarized in Table 14. The upper table shows the results for theextended period from January 2013, and the lower table shows the results for the period
after the implementation of QQE in April 2013. As there is only a small number of
events in the period between January and April 2013 (12 in the baseline event set and
3 in the alternative event set), the cumulative changes during the response windows are
generally not substantially diﬀerent between the upper and lower tables. In contrast,
the total cumulative changes through the two periods are very diﬀerent, as shown inthe bottom line in each table, because the zero-coupon yields decreased substantiallyin the period between January and April 2013 (23.8 basis points for 10-year yield)
and then lowered only slightly (3.1 basis points) after the implementation of QQE
until the end of our sample period.49 Therefore, while the eﬀects (cumulative changes
during the response windows) in the extended period (shown in the upper table) are
generally comparable with the total cumulative changes in the same period, the eﬀects
in the period after the implementation of QQE (the lower table) are much larger than
the total cumulative changes in the corresponding period. The latter implies that the................................
47. The corresponding dates of exercise of the operations are generally two working days after the oﬀer dates.
48. The market operations conducted in the period prior to April 4, 2013 include those under the asset purchaseprogram in “Comprehensive Monetary Easing” as well as those conducted as a regular operation tool.
49. After the end of the sample period (September 30, 2014), the long-term interest rates decreased substantiallyagain, especially after the expansion of QQE was announced on October 31, 2014. The decrease in the 10-yearzero-coupon yield from September 30, 2014 to March 31, 2015 was 13.2 basis points.

77

Table 14 Event-Study Analysis

Note: The table shows the cumulative changes in the zero-coupon yields and spreads during the response window of each events. One-day window is measured from the closing level of the working day prior to the offer date to the closing level of the offer date, and two-day window is measured from the closing level of the two working days prior to the offer date to the closing level ofthe offer date.

interest rates actually increased on non-event days reflecting many factors including
rising inflation expectations, a rebound in the economic outlook, and improvements inmarket risk sentiment.50
From the comparison between the alternative event sets and response windows, we
can see that the eﬀects in the two-day window of the alternative (narrower) event set
are the largest. This implies that the interest rates decreased remarkably on the day
before the oﬀer date of the outright purchases of JGBs with maturities over 10 years.
From the comparison between the interest rate measures, it is shown that the eﬀects
on the 20-year yield are larger than those on the 10-year yields, while the eﬀects on
the 10-year/3-year spread are larger than those on the 20-year/10-year spread. These
relationships are generally consistent with the total cumulative changes through theextended period from January 2013.
B. Results from Regression and Term Structure Model Approaches
We then show the results calculated from the analyses in Sections III and IV for theeﬀects of the BOJ’s JGB purchases and maturity extension on term spreads. As mentioned above, we plug in the BOJ’s contribution to the various net supply measures in
the regression equations and calculate the monthly cumulative net supply eﬀects. The................................
50. Similar results of the decomposition between event days and non-event days are also obtained in event-study
analyses using the U.S. data, such as Gagnon et al. (2011).

78 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

Table 15 Effects of the BOJ’s JGB Purchases

Note: In the regression approach, the effects of the BOJ’s maturity extension are presented, exceptthat the values in the angular brackets are the effects of the increase in the JGB purchases aswell as the maturity extension.

results are summarized in Table 15. The upper table shows the results for the extended
period from January 2013, and the lower table shows the results for the period from
April 2013. As in Table 14, the calculated cumulative eﬀects are generally not substantially diﬀerent between the upper and lower tables because the BOJ’s holding of JGBs
and its average maturity changed little in the period between January and April 2013.
The results for the term spreads from the regression approach in Section III are calculated using the estimated coeﬃcients in the baseline and an alternative specification(the baseline estimation shown in Tables 2 and 6 and the alternative specification using
the BOJ’s average maturity separately as shown in columns (iv) of Tables 3 and 7), andtwo sub-sample regressions with the baseline specification (the zero lower bound periods and the period after the global financial crisis as shown in columns (viii) and (ix)of Tables 5 and 9). In the baseline specification, we calculate the pure contribution of
the BOJ’s maturity extension (not including the contribution of changes in its share of
the outstanding JGBs) to the arbitragers’ average maturity, which is represented by thewhite bars in Figure 5 in Section II, and then multiply it by the estimated coeﬃcientson the (instrumented) arbitragers’ average maturity.
Regarding the eﬀect on the 10-year/3-year spread, the result using the baseline estimation is 11.0 basis points for the extended period, as shown in column (i) of Table 15.
The result from the alternative specification (column (ii)) is larger, possibly reflecting
the downward bias caused by the endogeneity problem remaining in the baseline result.
The results from the sub-sample regressions (columns (iii) and (iv)) are also larger thanthe baseline result, reflecting the larger estimated coeﬃcients. Regarding the eﬀect on
the 20-year/10-year spread, the result using the baseline estimation is 27.7 basis points
for the extended period. In contrast to the eﬀects on the 10-year/3-year spread, how-79

ever, the result from the alternative specification is smaller than the baseline result. As
a result, within these alternative specifications, the eﬀect on the 10-year/3-year spreadis larger than that on the 20-year/10-year spread, while the former is smaller using
the baseline estimation. Overall, these results obtained from the regression approach
are broadly comparable with the range resulting from the event-study analysis (column (vi)) and the actual changes in the term spreads through the extended period fromJanuary 2013 (column (vii)).
The results for the term spreads from the term structure model approach in Section
IV are calculated using the estimated coeﬃcients in the specification with the coeﬃcient dummies for the ZLB regime on the yield-curve factors (columns (i) of Tables 11
and 12). We calculate the contribution of changes in the maturity structure of JGBs
held by the BOJ to the model-implied net supply measure, and then multiply it by theestimated coeﬃcients on the net supply measure. In addition, we also take accountof the eﬀects of changes in the yield-curve factors on the term spreads under certain
assumptions about the relationship between the maturity structure and the yield-curve
factors.51 The results are shown in column (v) of Table 15 as ranges depending on theassumption of the above relationship. In both the results for the 10-year/3-year and20-year/10-year term spreads, the ranges of the eﬀects are relatively small comparedwith the results from the regression approach and the event-study analysis. This may
reflect the model estimation results in which the yield-curve factors are less volatileand the yields are less responsive to the yield-curve factors under the ZLB regime.
Finally, we calculate the eﬀect of the BOJ’s JGB purchases on the 10-year term
premium derived from the term structure model in Section IV. The term premium isdefined as the actual bond yield minus the average expected future short-term interest
rates over the life of the bond.52 Then the derived term premium is regressed on thearbitragers’ average maturity, the change in the ratio of the arbitragers’ holding JGBs
(less than 10 years) to nominal GDP, the equity premium, the consumer price index
inflation, the output gap, and the constant.53 The estimated coeﬃcients on the two net
supply measures, the arbitragers’ average maturity and the change in the arbitragers’
debt-to-GDP ratio, are both significantly positive. Using these estimated coeﬃcients,
we calculate the eﬀects of the BOJ’s JGB purchases and maturity extension on the 10year term premium. The result is shown in the bottom line in Table 15. The eﬀectof the maturity extension is 38.0 basis points and the eﬀect of the increase in the JGB
purchases as well as the maturity extension is 60.0 basis points (both for the extended................................
51. Specifically, we assume that the correlation between the maturity structure that was most influenced by the
BOJ’s JGB purchases and the first yield-curve factor is in the range between 0.1 and 0.6, judging from thedata.
52. To calculate the expectations components in the n-period term premium, we obtain 1, 2, . . . , n period forecastsof the future short-term interest rates at each month via two-regime three-variable VAR forecasting. See
Appendix 2 for details.
53. The estimation result is as follows:
10
10
3
5
6
tp10
t = 0.764 [3.20]xt + 118.2 [3.23]xxxt − 0.287 [−3.31]zt + 0.076 [0.76]zt + 0.067 [1.11]zt− 1.660 [−1.49] + ut ,10
3
10
where tp10
t is the 10-year term premium, and xt and zt are the same as in equation (1). xxxt is the change
in the ratio of JGBs (less than 10 years) held by the arbitragers to nominal GDP (smoothed by the Hodrick–
Prescott filter), z5t is the consumer price index inflation, and z6t is the output gap estimated by the OECD. The
values in the brackets are the Newey–West adjusted t-statistics. The adjusted R-squared is 0.497. The sample
period is from January 1992 to September 2014.

80 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

period). These results are broadly comparable with the cumulative changes in the 10year yield calculated in the event-study analysis shown in Table 14 (27.4 to 56.5 basis
points for the extended period).54

VI. Concluding Remarks
In this paper, we have examined how the net supply of JGBs aﬀected the term structure of interest rates and the risk premium on long-term JGBs using our constructed
database on the amount outstanding of JGBs categorized by holder and remaining maturity. Both approaches using single-equation regressions and a term structure model
confirm that the net supply of JGBs had significant eﬀects on long-term interest rates,
which is consistent with the preferred-habitat theory. The regression approach implies
that the net supply eﬀects were stronger in the zero interest rate periods, while thisrelationship was not found using the model approach. We also calculated the net supply eﬀects of the BOJ’s JGB purchases as part of the QQE using both approaches andcompared the results with those obtained from a simple event-study analysis.
Based on our analyses in this paper, several directions for future research could
be pursued. First, we have left the problem of when and how the eﬀectiveness of the
net supply of JGBs on long-term interest rates changed. A clear solution to this problem would provide useful implications for the future normalization of unconventionalmonetary policy as well as the government debt management policy. Second, there areseveral channels through which a shock to the net supply of JGBs aﬀects long-term
interest rates. It would be essential to empirically disentangle these channels for moreaccurately measuring the size, timing, and persistence of the net supply eﬀects. On
the theoretical side, there would be more room for improvement in specifications of
the preferred-habitat theory, including a consideration of some heterogeneity among
preferred-habitat investors, and for developing other theories on the eﬀects of a central
bank’s purchases of government bonds on long-term interest rates.55 Third, while we
focus mainly on the gradual and persistent changes in interest rates using monthly data,
daily or intra-day fluctuations and instantaneous responses to a net supply shock suchas the eﬀect of a central bank’s ongoing purchase operations are also important, as discussed in Section V. In this regard, how the scarcity channel captured in our analyses
relates to short-term liquidity would be an important problem left for future consideration. Finally, given the significant net supply eﬀects on long-term interest rates, somenormative and policy implications could be derived from this result. The current situation in Japan is that the BOJ extends the maturity of its holding of JGBs to achieve its
price stability target and the private preferred-habitat investors extend their maturity tomatch their long-duration liabilities, while the government extends the maturity of its................................
54. BOJ (2015) estimates the eﬀects of the BOJ’s JGB purchases on real interest rates using several approaches.
According to its regression approach, the cumulative eﬀect from March 2013 to December 2014 was minus
80 basis points in terms of 10-year yields. This result seems broadly comparable with our results on the nominal 10-year term premium, considering that the long-term inflation expectations of economists and market
participants increased by around 40 to 50 basis points during the corresponding period.
55. For instance, Williamson (2014) constructs a model in which short-maturity government debt has a greater
degree of pledgeability than long-maturity government debt and collateral is collectively scarce, in which casea central bank’s purchases of long-maturity government debt could flatten the yield curve.

81

debt to reduce the risks associated with refinancing. In terms of overall social welfare,however, there might be some room to improve the situation by pursuing better coordination among these entities.56 We hope that our analyses in this paper will serve as a
useful starting point for future research and policy discussions.

................................
56. Greenwood et al. (2014) discuss the government debt management policy in the U.S. and suggest revised
institutional arrangements to promote greater cooperation between the Treasury and the Federal Reserve when
the conventional monetary policy is constrained by the zero lower bound.

82 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

APPENDIX 1: Database on JGBs
In this appendix, we explain how to construct the database on the amount outstandingof JGBs categorized by holder and remaining maturity.
A type of JGBs that is used in our analyses throughout the paper is fixed-rate JGBs,
which cover the majority of the government debt in Japan (around 75 percent of thecentral government bonds and 60 percent of the general government gross debt as of2013). In particular, we use 2-year, 4-year, 5-year, 6-year, 10-year, 20-year, 30-year,
and 40-year fixed-rate JGBs. We do not use 15-year floating-rate bonds, inflationlinked bonds, financial bills, Treasury bills (T-bills), or any other discount bonds. We
exclude directly underwritten bonds and focus on marketable bonds. Besides the total issuance of JGBs, we consider three sectors: the Bank of Japan (BOJ), insurancecompanies, and pension funds. Regarding the maturity structure, we use face-value
outstanding of JGBs issued/held by each sector,57 and categorize them into six categories along with their remaining maturities:58 “less than or equal to 1 year,” “longer
than 1 year but less than 3 years,” “longer than 3 years but less than 5 years,” “longer
than 5 years but less than 7 years,” “longer than 7 years but less than 10 years,” and“longer than 10 years.” Our database has the form of a “sector (four)” by “maturity
category (six)” matrix for every end of month from January 1992 to September 2014,
which corresponds to the main sample period of our analyses. Due to unavailability of
data, for some sectors and some sample periods we estimate the maturity structure using the data on the total amount outstanding of JGBs held by the sectors. The overview
of our database and data availabilities is summarized in Table 16.
Using the above database, we calculate the average maturity of JGBs held by thearbitrager, which is used as a key net supply measure in our analyses. As explainedin Section II, we define “arbitragers” as investors excluding the BOJ, insurance companies, and pension funds. The average maturity of JGBs held by arbitragers is calculated as the weighted sum (or diﬀerence) of the average maturity of the total issuanceof JGBs, the BOJ’s average maturity, insurance companies’ average maturity, and pension funds’ average maturity.59 The weights are based on the share of JGBs held by
each sector. As explained later, our maturity structure data only cover the period from
September 2003 to September 2014 due to the data limitations. To calculate the arbitragers’ average maturities between January 1992 and August 2003, we assume thatthe maturity structure of JGBs held by each sector is exactly the same as that for the
total issuance. We calculate the arbitragers’ average maturity using the step adjustment
method for the period, and connect it with the data from September 2003 to September
2014.
In the following, we explain the detail of data construction method sector by sector.
................................
57. To avoid the endogeneity problem in our regression analyses, we basically use the data in face-value terms.
However, we cannot obtain some data of this type. In this case, we estimate it based on the data in marketvalue terms. The details are explained later.
58. It is possible to calculate the remaining maturities more precisely for the total issuance and JGBs held by the
BOJ. We use these six categories because data for insurance companies are only available in these categories.
59. The average maturity of JGBs with maturities less than 10 years held by the arbitragers are calculated in thesame way, except that data with maturities less than 10 years are used.

83

84 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Table 16 Overview of Our JGB Database and Data Availabilities

Maturity Structure and Supply Factors in Japanese Government Bond Markets

A. Total Supply
We collect the issuance data from the Ko-Shasai Binran (Japanese Bond Handbook)60
on every single JGB issued between January 1979 and September 2014.61 This
database provides data on the characteristics of each bond, including bond type, series
number, date of issue, date of redemption, amount issued in face-value terms, anddirect underwriter (if any).62 To focus only on marketable bonds, we exclude the datawith the direct underwriters. We also collect retirement by purchase data63 from the
Ministry of Finance to calculate the remaining JGBs outstanding.64 The data include
the bond type, series number, date of purchase, and the purchase amount in face-value
terms. Subtracting retirement by purchase data from the corresponding bond issuancedata, we calculate the remaining maturity and the remaining amount in face-value
terms for every single JGB for each end of month,65 and categorize the amount into
six maturity categories. Finally, we sum over all remaining bonds to build up the total
issuance data.
B. Bank of JapanThe BOJ has released statistics titled “Japanese Government Bonds held by the Bankof Japan” every month since June 2001.66 These statistics report the information on
JGBs held by the BOJ at the end of the previous month, including bond type, series
number, and amount of holding in face-value terms. These statistics do not include
JGBs that are directly underwritten by the BOJ.67 We combine these data and the bondcharacteristics data explained in Appendix 1.A and, in the same way as the total supply,
obtain a data series on the amount outstanding of JGBs with their maturity structuresfrom May 2001 to September 2014.
As we cannot know the maturity structure of JGBs held by the BOJ prior to May
2001, we instead construct the data on the total amount outstanding of JGBs held by
the BOJ between January 1992 and April 2001. The data in these periods are basedon the flow of funds statistics,68 which report the amount outstanding of JGBs held by
the BOJ in market-value terms.69 Using these statistics, we first interpolate the datalinearly, and calculate the year-on-year growth rate of JGBs held by the BOJ for eachmonth. Then we backwardly estimate the total amount outstanding of JGBs held by................................
60. The handbook is published semiannually by the Japan Securities Dealers Association (available only inJapanese).
61. We exclude bonds redeemed before 1992.
62. For example, the Financial Investment and Loan Program is one of the largest direct underwriters in our earlysample period.
63. We use only the data of retirement by purchase from the market. The data are available on the website of the
Ministry of Finance as part of its “Notification of the Ministry of Finance” (available only in Japanese).
64. As prematurity redemption of fixed-rate JGBs has never been observed in Japan, the amount outstanding ofmarketable fixed-rate JGBs only decreases when the Ministry of Finance conducts a retirement by purchaseother than the redemption at maturity.
65. We do not break the stream of each bond’s cash flows into principal and coupon payments to construct the
future cash flows as in Greenwood and Vayanos (2014).
66. The statistics are available on the website of the BOJ.
67. Before 1998, the BOJ directly underwrote JGBs to roll them over.
68. The statistics are available on the website of the BOJ.
69. The statistics include 15-year floating-rate bonds, inflation-linked bonds, and JGBs that were directly underwritten by the BOJ.

85

the BOJ in face-value terms given this growth rate and the data after May 2001.
C. Insurance Companies
The data on the total amount outstanding of JGBs held by insurance companies are
based on the flow of funds statistics. Since the data in flow of funds statistics are inmarket-value terms, we avoid using them directly. The detail estimation method is asfollows. After December 1997, we calculate the share of JGBs held by insurance companies in the net issuance of JGBs,70 and multiply this by the total amount of issuance inthe face-value terms we explained in Appendix 1.A. Before November 1997, due to thediscontinuity in the statistics, we first calculate the year-on-year growth rate of JGBs
held by insurance companies that are defined diﬀerently, and backwardly estimate thetotal amount outstanding of JGBs held by insurance companies given this growth rate
and the data after December 1997.
As for the maturity structure, we estimate it based on the disclosures of individual
insurance companies. Insurance business law in Japan requires every insurance company to disclose the amount outstanding of JGBs and T-bills71 by period remaining
at least once each business year.72 In the data, companies report six categories of theamount outstanding of JGBs and T-bills based on the remaining maturity mentioned
above. To estimate the maturity as precisely as possible, we consider separately the
structure of private life insurance companies, nonlife insurance companies, and Japan
Post Insurance.73 As for the maturity structure of JGBs held by private life insurancecompanies, we sum up the data for 11 major life insurance companies, and obtain theshares of each maturity category in the total amount outstanding of JGBs and T-bills
from September 2003 to September 2014, using linear interpolation and a seasonality adjustment method. The same method is applied for four major nonlife insurancecompanies and Japan Post Insurance, respectively.74 We then multiply this by the corresponding total amount outstanding of JGBs of these three insurance categories, respectively,75 and obtain the data on the amount outstanding of JGBs and T-bills categorized................................
70. The net issuance of JGBs is defined as the total issuance of JGBs minus the amount of JGBs held by government agencies.
71. The evaluation method of JGBs and T-bills is mixed, and it diﬀers along with the purpose of holding; bonds
declared as held-to-maturity debt are evaluated in terms of face value, and other securities are evaluated interms of market value.
72. Insurance companies disclose these data through annual or semiannual reports. Their reports are mostly
available on their homepage, but many companies release them only in Japanese.
73. We treat Japan Post Insurance, a subsidiary of the Japan Post, as a preferred-habitat investor in this paper. As
for Japan Post Bank, another subsidiary of Japan Post, we treat it as an arbitrager. Although its investment
strategy may be diﬀerent from that of other major banks, its average maturity is not substantially diﬀerent
from that of major domestic banks. In order to obtain marketable JGBs held by Japan Post Insurance, we
subtract the amount outstanding of directly underwritten JGBs from the total amount outstanding of JGBs
held by Japan Post Insurance. The amount outstanding of directly underwritten JGBs held by Japan Post
Insurance is estimated based on the Ko-Shasai Binran (Japanese Bond Handbook).
74. Since it is almost impossible to collect data from every insurance company in Japan, we only use the data ofmajor insurance companies, and assume them to be a representative value. We use the data of 11 major life
insurance companies and four major nonlife insurance companies besides that of Japan Post Insurance.
75. The total amount outstanding of JGBs in each insurance category is calculated exactly the same way as we
explained above, and the sum of the total amount outstanding of JGBs of these three categories is equal to thetotal amount outstanding of JGBs held by insurance companies. To obtain the total amount outstanding of
JGBs held by Japan Post Insurance, we use its disclosure as well as the flow of funds, because of discontinuity

86 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

by maturity structure from September 2003 to September 2014. Finally, we sum up
these three insurance categories, and subtract the total amount outstanding of T-bills
held by insurance companies, which is based on the flow of funds statistics, from theamount outstanding of JGBs and T-bills with maturities of “less than or equal to 1 year”
to obtain the amount outstanding of JGBs.
D. Pension Funds
The data on the total amount outstanding of JGBs held by pension funds are estimatedbased on the flow of funds statistics, which are in market-value terms as well. After
December 1997, we calculate the share of JGBs held by pension funds plus public pensions in the net issuance of JGBs, and multiply this by the total amount we explained
above. Before November 1997, due to the discontinuity in the statistics, we cannot
obtain exact data on pension funds. We assume that the share between 1992 and 1997
is equal to the average share of JGBs held by pension funds in the total issuance between 1997 and 2014. Using this assumption, we obtain the data on the total amountoutstanding of JGBs held by pension funds from January 1992 to September 2014.
As for the maturity structure, since there is no disclosure of JGBs’ maturity structure information in pension funds, we use as a proxy the maturity structure informationfrom the NOMURA Bond Performance Index, which is used by many pension funds
as a benchmark index for passive management of JGBs.76 The information is available
through the disclosures of fund-of-funds style investment trusts in which the index isused as an underlying fund. The annual disclosure reports the information on JGBs
held by the index, including bond type, serial number, and amount of holding in facevalue terms.77 We combine these data and the bond characteristics data explained inAppendix 1.A, and, in the same way as for total supply, obtain the data series on theamount outstanding of JGBs, categorized by maturity structure, using linear interpolation and a seasonality adjustment method, from May 2006 to May 2014. Since eachcategory of maturity structure in these periods is slightly changed with a constant slope,
we assume that the maturity structures from September 2003 to April 2006 as well asfrom June 2014 to September 2014 are equally changed like those between May 2006
and May 2014. Combining this assumption with the total amount outstanding of JGBs
held by pension funds, we can also calculate the data on the amount outstanding of
JGBs categorized by maturity structure in these periods.

..........................................................................................................................................
in the statistics.
76. For example, the Government Pension Investment Fund declares that it uses this index as a benchmark in its
annual disclosure.
77. We use information from the “Nomura Domestic Bond Index Fund Nomura BPI DC.” The data are available
through the Electronic Disclosure for Investors’ NETwork (EDINET) system in Japan.

87

APPENDIX 2: Term Structure Model in Section IV
In relation to Section IV in the text, this appendix summarizes the underlying modeland reports the estimated parameters in Table 17. For a full description of the model,
derivations, estimation strategy, and discussions on estimated results, see Koeda(2015). Following Vayanos and Vila (2009), we assume that there are two types of
agents in the government bond market: preferred-habitat investors and arbitragers.
Arbitragers maximize the mean-variance expected returns on their government bondportfolio, while preferred-habitat investors prefer to hold particular maturities ofgovernment bonds. The bond market equilibrium price is determined by equating
arbitragers’ net demand and preferred-habitat investors’ net supply for diﬀerent
maturities of bonds.
Specifically, the model follows a discrete-time version of Vayanos and Vila (2009)
discussed by Hamilton and Wu (2012a, HW henceforth). It extends HW by (i) allowing
the coeﬃcients in yield-curve factor dynamics as well as the prices of risk to change atthe zero lower bound (ZLB) regime to allow greater model flexibility, (ii) using latent
factors instead of observable factors to improve model fit to the data, (iii) writing out
the arbitragers’ portfolio optimization problem at the ZLB regime solving for the bondmarket equilibrium price, and (iv) carrying out estimation using JGB data.
Bond pricing in “normal” time (in the absence of the ZLB) follows the same specification as HW. HW define the arbitragers’ rate of return from period t to period t + 1
on their portfolio (rt,t+1 ) as:N

rt,t+1 =znt rn,t,t+1 ,

(7)

n=1

where znt is a fraction of their portfolio in the bond of maturity n and rn,t,t+1 is theholding-period return from period t to t + 1 on the n-period bond.
At the ZLB, arbitragers face two types of regimes: the ZLB regime where the ZLB
binds, and the normal regime where the ZLB does not bind (denoted by s = 0 and s = 1,
respectively). They maximize the mean-variance expected returns weighted by thetransition probability that the ZLB will continue to bind in the next period (π00 ) or that
it will be lifted (π10). These transition probabilities (πi0 for i = 0, 1) are assumed to be
exogenous and constant and add up to 1 ( i=0,1 πi0 = 1). The arbitragers’ optimization
problem at the ZLB regime can be expressed as:
πi0 [E rt,t+1 |st+1 = i, st = 0, f t

maxz1t ,...,zNt

i=0,1



− (γ/2) Var rt,t+1 |st+1 = i, st = 0, f t ],(8)subject toN

znt = 1,n=188 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015(9)

Maturity Structure and Supply Factors in Japanese Government Bond Markets

where γ captures the arbitragers’ risk aversion. f t are the yield-curve factors assumed
to follow a VAR (1) process as:
f t+1 = ci + Φi f t + Σi ut+1 ,with normalization that gives the identity matrix Σ1 and a 3 × 1 vector of zeros c1
and, for parsimonious purpose, we assume that Σ0 is a diagonal matrix. We can approximately solve for zt = (z2t , . . . , zNt ) , that is, the arbitragers’ demand equation.
zt depends on expected excess one-period holding returns on diﬀerent maturities ofbonds. Given zt , the arbitragers’ demand for the short-term bond, z1t , can be derived
by equation (9).
The preferred habitat’s net supply of bonds (xnt ) is modeled in the same manner as
the normal-time model, except that the supply-equation coeﬃcients are allowed to takediﬀerent values at the ZLB regime:0− α0n yt,n , for n = 1, . . . , N,
xnt ≡ ςt,n(10)0
= ςn0 + ϑ0n f t .
where yt,n is the log yield and ςt,n
By equating the demand and supply functions for each maturity of bonds, the equilibrium log bond prices can be derived as follows:

p0t,n = ā0n + b̄0n f t , for n = 1, . . . , N,ā0n = ā01 +πi0 āin−1 + b̄in−1 ci − Σi λi + (1/2) b̄in−1 Σi Σi b̄in−1 ,

(11)
(12)

i=0,1



πi0 b̄in−1 Φi − Σi Λi + b̄01 ,b̄0n =

(13)

i=0,1

with the prices of risk coeﬃcients given byN

λ = γΣ
ii

b̄in−1



ςn0 +



α0n /n



ā0n



N

, Λ = γΣ
i

i

n=2



 
b̄in−1 ϑ0n + α0n /n b̄0n .

n=2Thus, at the equilibrium, bond prices in the ZLB regime follow the standard aﬃneterm structure model with regime shifts. Furthermore, by arbitragers’ FOCs, it can beshown, the prices of risk can be expressed as a function of zt , as follows:N

λit ≡ λi + Λi f t = γΣiznt b̄in−1 .

(14)

n=2

89

Table 17 Estimated Parameters of the Term Structure Model in Section IV

Note: c1 and Σ1 are normalized to be a 3×1 vector of zeros and a 3×3 identity matrix, respectively.
Numbers in the parentheses are standard errors.

A. Risk Premium (Holding-Period Excess Returns)
At the bond market equilibrium, the model-implied expected k-period holding excess
log return of j-period bonds under the normal regime (rx1t+1, j,k ) can be expressed as:
E t rx1t+1, j,k ≡ E t p1t+1, j−k − p1t, j + p1t,k= E t ā1j−k + b̄1j−k f t+k − ā1j − b̄1j f t + ā1k + b̄1k f t ,N= c1j,k + Φ1j,k f t + γb̄1j−1 Σ1 Σ1

znt b̄1n−1 ,n=2

where p1t, j is the j-period log price. The second equality holds because bond prices aremodeled as an exponential aﬃne function of the yield-curve factors. The third equality
holds by using the recursive equations for ā1j and b̄1j and the arbitragers’ FOCs, and 
also by solving for the conditional expectation term E t ā1j−k + b̄1j−k f t+k with c1j,k ≡ kā1j−k + ā1k − ā11 − ā1j−1 − 12 b̄1j−1 Σ1 Σ1 b̄1j−1 and Φ1j,k ≡ b̄1k − b̄11 + b̄1j−k Φ1 − b̄1j−1 Φ1 .
Similarly, the corresponding excess log return under the ZLB regime can be
expressed as:

90 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond MarketsE t rx0t+1, j,k ≡ E t p0t+1, j−k − p0t, j + p0t,k


t+k
t+k
= E t ā sj−k
+ b̄sj−k
f t+k − ā0j − b̄0j f t + ā0k + b̄0k f t ,N= c0k + Φ0k f t + γ

πi0 b̄ij−1 Σi Σi
i=0,1

znt b̄in−1 ,
n=2

where
⎧
⎫
k 
⎪
i−1 ⎪
⎪
⎪
⎨
⎬
ā0 +
+ (1 − π00 ) ā1j−kΦ0c0 ⎪c0k ≡ ā0k − ā01 + (π00 )k ⎪
⎪
⎪
⎩ j−k
⎭
i=1
⎛
⎞
k−1
⎜⎜⎜
 k−l l  i−1 ⎟⎟⎟(π00 )l (1 − π00 ) ⎜⎜⎜⎝ā1j−k + Φ1+
c0 ⎟⎟⎟⎠
Φ0
i=1
l=1


i
i
i
i
−
πi0 ā j−1 + b̄ j−1 c + (1/2) b̄ j−1 Σi Σi b̄ij−1 ,
i=0,1

 k
 k
Φ0k ≡ b̄0k − b̄01 + (π00 )k b̄0j−k Φ0 + (1 − π00 ) b̄1j−k Φ1k−1+

 k−l  l(π00 )l (1 − π00 ) b̄1j−k Φ1
Φ0 −

l=1

πi0 b̄ij−1 Φi .
i=0,1

B. Term Spread
The model-implied j-period log bond price under the normal regime can be expressed
as:p1t, j = c1j−1 + Γ1j−1 f t − b̄1j−1 Σ1 λ1t , for j = 1, . . . , N,N

= c1j−1 + Γ1j−1 f t − γb̄1j−1 Σ1 Σ1

znt b̄1n−1 ,n=2

where the first equality holds by the pricing equation (equations (11)–(13)) andthe second equality holds by the arbitragers’ FOCs with c1j−1 ≡ ā1j−1 + b̄1j−1 c1 +1 1
1 1 11
1
1
1
12 b̄ j−1 Σ Σ b̄ j−1 +ā1 and Γ j−1 ≡ b̄ j−1 Φ + b̄1 . This implies that the term spread between
j- and k-period bonds ( j > k) can be expressed as:N
1yt, j − yt,k = c̃1j,k + Γ̃ j,k f t + γ (1/ j) b̄1j−1 − (1/k) b̄1k−1 Σ1 Σ1
znt b̄1
n−1 ,
n=2
1

where yt, j = −p1t, j / j, c̃1j,k ≡ c1k−1 /k − c1j−1 / j, and Γ̃ j,k ≡ (1/k) Γ1k−1 − (1/ j) Γ1j−1 .
Similarly, the j-period log bond price under the ZLB regime can be expressed as:Np0t, j = c0j−1 + Γ0j−1 f t −γπi0 b̄ij−1 Σi Σi
i=0,1

znt b̄in−1 , for j = 1, . . . , N,
n=2

91




where c0j−1 ≡ ā01 + i=0,1 πi0 āij−1 + b̄ij−1 ci + (1/2) b̄ij−1 Σi Σi b̄ij−1 and Γ0j−1 ≡ii0i=0,1 πi0 b̄ j−1 Φ + b̄1 . Then the term spread between j- and k-period bonds can be
expressed as:
⎛

⎞

N
⎜⎜⎜
⎟⎟⎟


0
0
i
i
i i
⎜
⎜
yt, j − yt,k = c̃ j,k + Γ̃ j,k f t + γ ⎜⎝πi0 b̄ j−1 / j − b̄k−1 /k Σ Σ
znt b̄in−1 ⎟⎟⎟⎠ ,
i=0,1
n=2
0

where yt, j = −p0t, j / j, c̃0j,k ≡ c0k−1 /k − c0j−1 / j and Γ̃ j,k ≡ (1/k) Γ0k−1 − (1/ j) Γ0j−1 .
C. Term Premium
We decompose the long-term bond yields into the expectations and term premium components. Following the typical definition in the literature, the term premium of ann-period bond yield is defined as the actual n-period bond yield minus  theaverage expected future short-term interest rates over the life of the bond (i.e., 1n E t n−1
j=0 r1,t+ j ).
To calculate the expectations components, we first obtain 1, 2, . . . , n period forecasts ofthe future short-term interest rates at each month via two-regime three-variable VAR
forecasting. Our model assumes that (i) if the initial regime is normal, then the corresponding VAR forecasting is reduced to a simple one-regime VAR forecasting. And(ii) if the initial regime is ZLB, then the regime shifts from ZLB to normal with theprobability of 1 − π00 in the next period; once the regime shifts to normal, however,it remains normal for the rest of the forecasting period. This implies that there aren + 1 possible paths of regimes and expected future yield-curve factors when the initial regime is ZLB. The conditional expectation on n-period ahead yield-curve factors
is computed by taking the average of possible values of expected yield-curve factors
weighted by probability.

92 MONETARY AND ECONOMIC STUDIES / NOVEMBER 2015

Maturity Structure and Supply Factors in Japanese Government Bond Markets

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