Misconceptions Regarding
the Zero Lower Boundon Interest Rates
Keynote Speech by Bennett T. McCallum

The paper reviews issues related to the zero lower bound (ZLB) on interest
rates and argues that all of the following propositions are invalid: (1) in a
ZLB situation, “shaping interest rate expectations is essentially the only
tool that central bankers have” (Bernanke, Reinhart, and Sack [2004]);(2) fiscal policy actions such as “helicopter drops” are in theory more
effective than monetary policy actions; (3) the prominent “foolproof way”
policy rule of Svensson (2001, 2003) is applicable more generally—that
is, even when exact uncovered interest parity holds—than the alternative
exchange rate rule of McCallum (2000); (4) both of the exchange rate
strategies described in (3) are open to the objection that they constitute“beggar-thy-neighbor” approaches; and (5) there is a significant danger of
ZLB difficulties stemming from a “deflationary trap” type of equilibrium,
as distinct from a “liquidity trap.”
Keywords: Interest rates; Zero lower bound; Quantitative easing;
Expectations; Deflation trap; Liquidity trap
JEL Classification: E3, E52, F41

Carnegie Mellon University (E-mail: bmccallum@cmu.edu)
I am indebted to Marvin Goodfriend for helpful comments.
MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006
DO NOT REPRINT OR REPRODUCE WITHOUT PERMISSION.

13

I. Introduction
It is highly appropriate that the Institute for Monetary and Economic Studies haschosen a conference topic relating to the interaction of financial market and macroeconomic phenomena in a setting with very low interest rates, with special consideration given to recent experience in Japan. In studying this topic, as with most issues
relating to policy, it is important to make use of structural models designed to mimic
the behavior of real-world agents and markets. Accordingly, there needs to be someagreement about the nature of the relevant monetary and macroeconomic framework,
as well as the nature of the Japanese experience.
There has been much progress during the past few years in the economics
profession’s understanding of the zero-lower-bound (ZLB) constraint on nominalinterest rates and its implications for the conduct of monetary policy. Recent workby Auerbach and Obstfeld (2003, 2004), Eggertsson and Woodford (2003, 2004),
Svensson (2001, 2003), Iwamoto (2005), Baba et al. (2005), Fujiwara et al. (2005),
Jung, Teranishi, and Watanabe (2005), and others has been noteworthy andconstructive in this respect. There are still a few impressions, however, that seem to
me to be rather widely held and yet somewhat misleading. My talk will be about
these. It will draw upon useful recent overview papers by Bernanke and Reinhart(2004) and Ueda (2005). I will not be offering any fundamentally new theoreticalresults, but will try to mention some points that might be of relevance in interpretingthe experience of the past decade in Japan.
The main objective will be to argue that all of the following propositions areinvalid or at least dubious: (1) in a ZLB situation, “shaping interest rate expectations
is essentially the only tool that central bankers have” (Bernanke, Reinhart, andSack [2004]); (2) fiscal policy actions such as “helicopter drops” are in theory more
effective than monetary policy actions; (3) the prominent “foolproof way” (FPW)
policy rule of Svensson (2001, 2003) is applicable more generally—that is, evenwhen exact uncovered interest parity (UIP) holds—than the alternative exchange
rate policy rule of McCallum (2000); (4) both of the exchange rate strategies
described in (3) are open to the objection that they constitute “beggar-thy-neighbor”
approaches; and (5) there is a significant danger of ZLB difficulties stemming froma “deflationary trap” type of equilibrium, as distinct from a situation involving a“liquidity trap.” These five topics will be discussed in Sections II–VI, with Section
VII providing a brief conclusion.

II. Monetary Policy Stimulus at the ZLB?
For discussion of currently prevailing views regarding monetary policy at the ZLB,
I will take as representative the recent overview paper of Bernanke and Reinhart(2004). This choice is warranted not only because the authors are leading policymakers for the Federal Reserve—even more so now than in 2004 when the paper waspresented!—but also because Bernanke has written on the topic earlier (Bernanke[2000]) and because the Bernanke-Reinhart paper has been treated as indicative of

14 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

prevailing views by Ueda (2005), who was himself a major participant in thepolicymaking process at the Bank of Japan during much of the ZLB episode. In theirpaper, Bernanke and Reinhart (2004, p. 85) “discuss three strategies for stimulating
the economy at an unchanged level of the policy rate.” Their list includes (a) shaping
interest rate expectations, (b) altering the composition of the central bank’s balance
sheet, and (c) expanding the size of the central bank’s balance sheet. The first of theseis the approach featured by Eggertsson and Woodford (2003, 2004), who develop an
irrelevance proposition for open market purchases according to which “quantitativeeasing” is to no avail. Instead, “the key to effective central-bank action to combat a
deflationary slump is the management of expectations ” (2003, p. 8). At face value, this
proposition seems to contradict results by Auerbach and Obstfeld (2003, 2004),
Coenen and Wieland (2003), and others who find a role for open market purchasesof “unconventional” assets.1 It will be argued below, however, that there is no actual
theoretical inconsistency; that the different papers presume different types of policy
experiments. Eggertsson and Woodford (henceforth, E&W) have argued that the
crucial distinction is whether or not the policy experiment considered involves apermanent change in some nominal variable. In that spirit, it will be shown belowthat if there is a credible rule change that, for example, increases the target inflation
rate, then monetary policy can be effective in bringing an economy out of a ZLB
situation even under the E&W assumptions.
The exact nature of the E&W result deserves attention. It involves analysis of
the stabilization properties of an interest rate policy regime that is specified to incorporate “quantitative easing.” That term is taken by E&W (2003) to mean that themonetary base supply function, which implements their interest rate rule with given
money demand behavior, includes an unusual nonlinear component that calls for
extra open market purchases whenever the interest rate is zero. These purchases are
immediately reversed, however, as soon as the interest rate rises above zero (theinterest rate in question, here denoted R t , is “the riskless nominal interest rate on
one-period obligations” from E&W [2003, p. 10]). One could simply view this
supply function as a policy rule for the monetary base, recognize the base moneystock as a variable, and solve the model in a standard and familiar fashion, if it were
not for the nonlinear component and the associated restriction that the interest rate
must be non-negative.2 What E&W do with the resulting model is to show that the
behavior of prices and output in the model’s rational expectations (RE) equilibriumis independent of any parameters that describe the quantitative easing componentof the base supply rule. Whatever the extent of the additional base-money supply
specified by this component, then, there will be no effect on inflation or output in
the RE equilibrium. That is the E&W irrelevance proposition. Note, crucially, that it
pertains to the nature of a single ongoing RE equilibrium for a given policy rule thatinvolves certain specified behavior when the ZLB is operative, not to the adoption of
1. Assets, that is, that are not perfect substitutes for the short-term security that is normally used in open market operations. The Bernanke-Reinhart list does not include Goodfriend’s (2000, pp. 1013–1018) suggestion of institutionalchanges to eliminate the ZLB.
2. The model used by E&W is rather standard, relative to the recent monetary policy literature, but is slightly more“monetarist” than is usual in that the utility function, which includes real money balances as an argument, is notassumed to be separable.

15a new rule. The irrelevance proposition is perhaps unsurprising, given that any “extra”
base money supplied (when R t = 0) is removed immediately, as soon as R t > 0.3
It is, I believe, somewhat misleading for the E&W analysis to be described in termsof shaping interest rate expectations; instead, it is expectations of future values moregenerally—not just interest rates—that matter. In particular, expectations regarding
future monetary aggregates or price levels could alternatively be made the focus of
expectations management. Svensson (2004) develops this point very effectively.
To emphasize the importance of policy rule changes that pertain to features of therule other than the special nonlinear component, let us briefly discuss an extremely
simplified example based on the following two-equation system, which is so familiar
as to require only a brief explanation at this point:4
yt = b 0 + b 1(R t – Et pt +1) + Et yt +1 + vt ,b 1 < 0,(1)

R t = 0 + pt + 1(pt – * ) + 2yt ,1 > 0, 2 ≥ 0.

(2)

Here yt and pt denote the logs of an output variable and the price level so that pt is
inflation while R t is the one-period nominal interest rate. The term vt represents apreference shock that is generated by an exogenous stochastic process, which isassumed to be autoregressive of order one with parameter ,  < 1. Equation (2) isa Taylor-style rule in which the central bank is depicted as setting an interest rate
instrument R t each period so as to tighten policy when inflation exceeds its target
value * and/or when output is high. In (1) and (2), yt should be interpreted as theoutput gap with the natural rate of output assumed constant at the value zero. With
flexible prices, we then have yt = 0 in each period and there are only two endogenous
variables to be determined by the system, R t and pt . This model should be understood to also include the requirement that pt must not approach –  as t → ,
because of a transversality condition that obtains in the underlying optimizing model.
To obtain an RE solution in the absence of any ZLB constraint, we first substituteout R t , use yt = 0, and assume that the central bank sensibly sets 0 to equal the
long-run real rate of interest r = –b 0/b 1. Then the relevant solution is 5
pt = * − [b 1(1 −  + 1)]−1vt .

(3)

When the constraint R t ≥ 0 is included, (3) is not in general the solution, but it willbe (to a suitable approximation) if vt has bounded support and the target inflation
rate * is large enough relative to r. Then suppose that the economy is initially ina ZLB situation, but the central bank adopts a new policy rule such that * issufficiently high so that the ZLB will never be binding in the future. In that case,
3. It is my impression that proponents of quantitative easing for Japan have almost invariably had in mind a newpolicy that, among other features, would entail a target inflation rate that is higher than values experienced inJapan during the ZLB episode—and certainly high enough to imply a positive steady-state interest rate on
overnight bank loans. Thus, their recommendations would have implied a change in the policy rule.
4. The present system differs from the model of E&W, but without the quantitative easing feature, primarily bypositing flexible prices, which is irrelevant to the point at issue.
5. See McCallum (2005, pp. 5–6), plus the discussion in Section VI below.

16 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

the new RE equilibrium will yield immediately an inflation rate high enough toescape the ZLB situation. Of course, it is rather implausible that such a new policy
rule would be credible immediately, but that is another issue that we will touch upon
below. The point here is to illustrate the major difference between a change in the
inflation target, on the one hand, and a change in a parameter such as 1 in (2).
The latter type of change would typically be ineffective in a ZLB situation becauseof the constraint that prevents any reduction in R t . This latter type of change is, in
effect, what is being shown to be useless by the E&W policy irrelevance proposition.
With respect to Bernanke and Reinhart’s (2004) strategy type (c), expanding thesize of the central bank’s balance sheet via open market purchases, I would like tocomment on their identification of this category with the term “quantitative easing.”
It is my impression that the latter term was introduced in the context of the Japaneseexperience, and with respect to proposals made by critics of the Bank of Japan’s actual
policy including, for example, Goodfriend (1997), Taylor (1997), Meltzer (1999a),and (especially) Nakahara.6 It is my further impression that these individuals hadin mind money creation together with the purchase of nonstandard assets, so that
their proposals actually amounted to applications of strategies (b) and (c) together.
By the late 1990s, it was widely understood that open market purchases of shortterm government bills would have no expansionary impact, as these assets becomenear-perfect substitutes for base money when an economy is in a ZLB situation.
In addition, I believe that they intended that the Bank of Japan also make public a
commitment to conduct policy so as to avoid deflation, in both the present and thefuture.7 Thus, their proposals might be interpreted as implying rule changes of thetype discussed above, which (if credible) would in theory have been effective (viastrategy [a]). The extent to which the large expansion of the Bank of Japan’s balance
sheet during 1999–2005 met these proposals is a matter of continuing discussion.

III. Fiscal Transfers
Some analysts (e.g., Ball [2005]) have suggested that a “helicopter drop” type ofpolicy, in which transfers of money are given to the public in a lump-sum fashion,
would be more effective than nonfiscal monetary policy actions for escaping a ZLB
situation. Is this position in fact supported by formal analysis? Here I argue very
briefly that such a policy would be ineffective if the economy possesses Ricardian
properties, as in the case of the canonical model used by E&W (2003) and manyothers. The first step of the argument is as follows.
A “helicopter drop” is a transfer (gift) of money to households. In this regard, notethat a transfer of $K is equivalent to the combination of two operations, namely,(1) a lump-sum tax reduction of $K financed by the sale of $K of T-bills to households
6. Nobuyuki Nakahara served on the Bank of Japan’s Policy Board through much of the episode and offered many
proposals at the Bank’s Monetary Policy Meetings, almost all of which were voted down.
7. See, for example, Goodfriend (1997, p. 294) and Meltzer (1999a, p. 190). The proposals of Goodfriend and Taylor
were presented at the seventh International Conference held in October 1995 by the Institute for Monetary andEconomic Studies of the Bank of Japan.

17

(i.e., a gift of $K of T-bills to households), and (2) an open market purchase of$K worth of T-bills. But it is well known that an operation of type (1) has no effect if
the economy is Ricardian and also that one of type (2) has no effect at the ZLB (wherebase money and T-bills are perfect substitutes at the margin). Thus, the combined
operation—the helicopter drop—will have no effect in the ZLB situation.
The second part of the argument pertains to a sequence of such operations. Would
not an ongoing sequence of helicopter drops violate a transversality condition if there
were no inflationary effect, since the nominal money stock would be growing withoutbound in the proposed experiment? Well, yes, it would if the ZLB situation were to
go on forever. But analysis of ZLB issues typically pertains to situations in which an
economy, assumed to have a positive steady-state nominal interest rate, is temporarily
at the ZLB as the result of some negative shock.8 In such cases, the economy will escape
the ZLB of its own accord at some point in the finite future, after which time pt
will tend to grow in line with m t , the log of the money stock. So, since transversality
conditions pertain only to the infinitely distant future, they are not relevant to thequestion at hand.
Of course, the foregoing analysis does not deny that one could obtain effects fromrepeated helicopter drops by using a non-Ricardian model, such as the overlappinggenerations model considered in McCallum (2000, pp. 876–880). Also, the argument
presumes, perhaps incorrectly, that the T-bills under discussion do not provide “broadliquidity” services, of the type mentioned by Goodfriend (2000, pp. 1018–1028).

IV. The Exchange Rate Channel
In a conference paper of 1999 (McCallum [2000]), I proposed a strategy whereby
central banks can avoid policy impotence at the ZLB via purchases of foreignexchange by using the exchange rate in place of the usual overnight interest rate as
the policy instrument/indicator variable. My paper argued, by means of simulations
with a quantitative model, that a policy rule for setting the exchange rate’s rate ofdepreciation, in response to inflation and output deviations from target values, could
provide macroeconomic stabilization even if the interest rate were immobilized at zero.
Subsequently, Svensson (2001) put forth a closely related proposal—which he called
the “foolproof way” (FPW)—involving the exchange rate transmission channel.
Svensson’s presentation was evidently much more effective than mine, as his paper has
attracted a good bit of attention whereas mine is mentioned rather infrequently.
Svensson (2001, p. 298) has explicitly recognized the close kinship of our two proposals, but has stated that his argument “does not depend on any portfolio-balance
effects of foreign-exchange interventions, in contrast to the argument of Meltzer(1999d) and McCallum (1999), and thus, it is more general.”9 It is my contention,
however, that our two policy rules are equally open to the objection—an objectionthat I consider inappropriate—that they rely on portfolio-balance effects. Instead,the policy rules evidently rely upon departures from pure UIP to exactly the same
8. Justification for this practice is discussed in Section VI below.
9. The papers cited are listed in the references below as Meltzer (1999b) and McCallum (2000).

18 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

extent; the main difference in the two proposals being that one is concerned with a shift
in policy while the other involves the effectiveness of one ongoing rule.
To make this argument, let us consider the following model of a small open economy. This model, developed by McCallum and Nelson (1999), differs (inessentially)
from most small-scale optimizing models by treating imports as raw materials used in
the production process rather than consumer goods that differ from the bundle ofdomestically produced goods. It can be summarized with the following 10 equations,in which st is the log of the home-country price of foreign exchange:
ct = Etct +1 + b 0 − b 1rt + vt ,b 1 < 0,yt =  1 ct +  2 g t +  3 xt ,0 <  1,  2 ,  3 < 1, (5)(4)

q t = st − pt + ptF,

(6)

im t = yt − q t + const,

 > 0,(7)xt = ytF +  Fq t + const,

 F > 0,(8)

y–t = (1 −

0<

(9)

)−1[ 1at −  2q t ] + const,2pt = (1 + )−1[ Et pt +1 + pt −1] + (yt − y–t ) + ut ,

2

< 1,

> 0, 0 < < 1, (10)R t − R tF = Et st +1 + t ,(11)

rt = R t − Et pt +1,(12)

R t = r + pt + 1(pt − * ) + 2(yt − y–t ) +t,

1, 2 ≥ 0.

(13)

A very brief description of each of these relationships will be provided. Equation (4)is a consumption (ct ) Euler equation, reflecting intertemporal optimization, while(5) is a log-linear approximation to an identity that splits units of output yt —notvalue added—into three components reflecting uses: consumption, government
consumption g t , and exports xt .10 Equation (6) defines the log of the real exchange
rate q t in relation to the log of the nominal exchange rate st and the logs of homeand foreign price levels, pt and ptF. Next, in (7) import demand im t is given by cost
minimization for a production function of the CES type with  as the elasticity of
substitution between imports and labor. An analogous relation (8) governs demand
from abroad for home-country exports. Equation (9) specifies the natural rate (i.e.,
flexible-price) value of the log of real output, y–t , with this value depending upona stochastic term a t that reflects the results of technology shocks (assumed to follow
an exogenous AR(1) process with autocorrelation parameter 0.95) and the real priceof imported inputs to production. A variant of the Calvo model of nominal price
10. That yt reflects units of output, not value added, is apparent from the production function used in (7) and approximated in (9). Domestic investment would also be included in a model that distinguishes between consumption
and investment spending. In the model, all variables except interest rates are logs of the underlying measures.

19

stickiness appears as (10) while (11) represents UIP, with a stochastic disturbance.
Finally, (12) is the Fisher identity that defines the one-period real rate of interest rt in
relation to the nominal rate R t and expected inflation.
Together with the Taylor-style policy rule (13), this model provides 10 structural
equations to generate values of the system’s 10 endogenous variables, namely, ct , yt , gt , xt ,imt , pt , st , qt , Rt , and rt . Now suppose that the interest rate instrument R t is immobilized
at the ZLB and thus is constant over time. In such a case, McCallum (2000) suggeststhat the central bank use as its instrument the exchange rate, with a rule such as
st − st −1 = q + pt − 1(pt − * ) − 2(yt − y–t ) − et ,1, 2 ≥ 0,

(13′)

where q is the average rate of depreciation of the real exchange rate. This policy rulecalls for purchases or sales in the foreign exchange market, rather than the overnightinterbank market, when macroeconomic conditions call for a loosening or tighteningof policy. In my paper, I presented simulations indicating that such a rule would be
effective in stabilizing inflation and/or output relative to their target values, despite
the immobilization of the interest rate.
Note, however, that if we assume that R t continues to equal zero in each period, thesystem becomes overdetermined when (13′) is included (or when [13] is included).
Accordingly, in the simulations I ignored the UIP condition (11). The justification forthis step is explained below. But the point at hand is that exactly the same issue arises
if instead of (13′) we adopt the policy rule of Svensson’s FPW strategy, say,st = s fpw + t,(13′′)

where  is the specified rate of depreciation and t indexes the passage of time, whiles fpw is a start-up value. In that case, if R t = 0 is maintained, the system becomes
overdetermined unless some equation from (4)–(12) is dropped or some otherendogenous variable is recognized. But Svensson (2001, p. 297) states that application of the FPW would have the central bank raising R t above the ZLB to “a level
corresponding to uncovered interest parity.” In his scenario, this jump occurs
promptly and there is no overdetermination because R t = 0 is not maintained. Thus,
the crucial difference in Svensson’s argument and mine is that he discusses the effects
of a rule change that immediately eliminates the liquidity trap, whereas my discussion
pertains to the performance of an ongoing rule under the constraint of an immobilized interest rate. If my rule were adopted anew, it could and should be designed to
imply (if instantly credible) a jump in conditions that would end the R t = 0 episode,just as in the case of the FPW. Then the UIP condition could be retained in theanalysis, if the analyst believed it to be realistic.11
Thus, we see that my analysis involves the workings of an ongoing policy rule
whereas Svensson’s featured the adoption of a new rule, with the two rules designed
11. It appears that the distinction between “foreign exchange interventions” and commitments to buy and sell foreignexchange at a stated price, mentioned in several places by Svensson (2001), is not pertinent. The latter methodof implementation could be used with my rule (13′) just as with the FPW, even if the quoted price is varied fromperiod to period in response to current conditions (rather than growing steadily).

20 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

to exploit the same transmission mechanism, working through the foreign exchange
rate. Since a major objective in each case was to argue that Japan could use thismechanism to improve macroeconomic conditions, it is clear why Svensson chose as
he did. What then, was the reason for my choice? In fact, my choice was predicatedon the belief that use of the RE condition is much more appropriate for the analysisof ongoing policy regimes than for the analysis of paths resulting from changes in apolicy rule. It seems unlikely, that is, that any policy rule change will immediately beknown about, believed, and understood, which is the implicit assumption for thelatter type of exercise. In this respect, my practice was consistent with the position ofLucas (1980).12
To complete this discussion, let us briefly consider whether the E&W irrelevanceproposition applies to a case in which the policy rule (13′) is maintained by thecentral bank in a ZLB situation. In this context, it does matter whether pure UIP
prevails, or instead equation (11) in the foregoing model needs to be modified torepresent some type of portfolio-balance effect. This can be done by assuming thatthe disturbance t in (11) is not exogenous, but instead is related to the relative
amounts of outside domestic and foreign nominal liabilities outstanding as int= [Bt − (BtF + st )] + t ,where Bt and BtF are logs of domestic and foreign government debt (including basemoney) and t is exogenous. Substituting and recognizing that lags could be involved,
we then write
R t −R tF = (Et st +1 − st ) + (L)[Bt −BtF − st ] + t ,(11′)

to replace (11). (Here (L) is a polynomial in the lag operator.) With this adjustment,
the model features additional state variables, relative to the case in which pure
UIP holds, and is therefore not one to which the E&W (2003, 2004) invarianceproposition applies.13

V. Beggar-Thy-Neighbor Effects?
An objection to both of the proposals discussed in the foregoing section, raised byseveral commentators, is that use of the exchange rate transmission channel would
probably be highly unpopular with nations that constitute the relevant country’s
trading partners, since exchange rate depreciation would improve its trade balance
and thereby reduce the country’s imports from its trading partners.14 For this reason,such strategies have been said to rely upon “beggar-thy-neighbor” effects that are
globally undesirable and politically objectionable. The premise of this argument is
12. In McCallum (2005), I modify the rule to make it effective in normal circumstances, as well as in a ZLB situation.
13. For additional discussion of the specification (11′), see the Appendix.
14. This frequently heard objection is studied by Coenen and Wieland (2003) and mentioned (without endorsement)
by Bernanke, Reinhart, and Sack (2004).

21

highly dubious, however, for a successful anti-ZLB policy will prevent a decline or
stagnation in a country’s real income level, which is the most important determinantof its imports. Furthermore, the exchange rate responses induced by a policy rulesuch as (13′) above pertain to nominal exchange rates and will have only temporary
real effects, other than those working through income, if the rule is effective instimulating demand. Quantitative simulation results exemplifying this claim arereported as a major feature of McCallum (2003, pp. 16–23) for an expansionary
increase in the target inflation rate *, with policy being conducted via the exchange
rate rule (13′).15 Svensson (2003, pp. 163–164) also discusses this point. In a more
recent contribution, he develops an argument indicating that use of the exchange ratetransmission channel will not have different import-export effects than any othermonetary policy action, for the same degree of demand stimulus (Svensson [2004,
pp. 91–92]). In sum, the “beggar-thy-neighbor” objection to use of the exchange ratechannel to escape ZLB difficulties seems to be fundamentally unjustified.

VI. The Deflationary Trap
Finally, I turn to the topic of the “deflationary trap” possibility, extensively discussed
by Benhabib, Schmitt-Grohé, and Uribe in a series of papers including Benhabib,
Schmitt-Grohé, and Uribe (2001, 2002). In this series, these authors have suggested
that a ZLB situation could arise for reasons quite different from those presumed above.
In the analyses of Krugman (1998), E&W (2003, 2004), Auerbach and Obstfeld(2004), Coenen and Wieland (2003), and most other writers on the ZLB issue, it isassumed that the relevant RE solution is one in which inflation normally fluctuatesaround the target value specified by a standard, Taylor-style, interest rate policy rule.
The discussions of Iwamoto (2005) and Fujiwara et al. (2005), however, consider as well
the possibility of a deflationary-trap equilibrium. An example taken from McCallum(2002) that assumes flexible prices and abstracts from stochastic shocks is given in
Figure 1. There the dark upward-sloping line has slope 1 + 1, representing rule (13)above, and the usual equilibrium is at this line’s intersection with the 45-degree line
(e.g., at * in Figure 1). If the target inflation rate (* ) plus the steady-state real rate ofinterest (r ) is a moderately high value, such as 4–5 percent per year, unusually large
shocks would then be required to push the system away from the * equilibrium to thevicinity of the ZLB for R t , where inflation pt equals −r. In contrast, Benhabib,
Schmitt-Grohé, and Uribe suggest that there are multiple RE equilibria and therelevant one may instead approach or be located at point A, even in the absence ofshocks. It is true that the latter pattern satisfies the first-order conditions for optimality,
and also the relevant transversality condition. Nevertheless, my position, argued mostextensively in McCallum (2002), is that this ZLB equilibrium is not plausible, because
it fails to be E-stable in the sense developed by Evans and Honkapohja (2001). Such a
15. Partially contradictory results are briefly reported by Coenen and Wieland (2003), but their policy experimentis quite different (with no policy response until after the ZLB constraint has been in effect for 10 quarters).
In addition, their model’s treatment of trade flows is somewhat problematic, as it does not recognize distinct
import and export quantities.

22 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

Figure 1 The Possibility of a Deflationary-Gap Equilibrium
∆pt

π*
0

−r

A

−r

0

π*

∆pt −1

failure implies that this (apparent) RE equilibrium would not be learnable in a settingthat recognizes that individual agents are not miraculously endowed with knowledgeof the economy’s parameters, but need to learn about them over time by observation of
the economy’s behavior. The usual RE equilibrium, focused upon by the other papers
mentioned above, is by contrast E-stable and learnable under standard assumptions.16
On the basis of this contrast, I would argue that the usual RE equilibrium is the only
one of these two candidates that is plausible as a description of the behavior of an actual
economy, so that it is highly unlikely that a ZLB situation would develop unlessmonetary policy lets * +r fall too close to zero.17

VII. Conclusion
Let me conclude with a very brief summary. This paper argues that, in contrast withthe beliefs of some analysts, (1) there are strategies for escaping ZLB situations otherthan “shaping interest rate expectations”; (2) fiscal transfers are in theory no more
effective than open market monetary policy actions under assumptions implying
Ricardian equivalence; (3) the difference between Svensson’s (2001) FPW rule andthe exchange rate policy rule of McCallum (2000) does not involve assumptions concerning UIP, but rather the type of policy experiment considered; (4) it is likely thatneither of the exchange rate strategies in (3) would lead to “beggar-thy-neighbor”
effects; and (5) the deflationary-trap type of ZLB equilibria are much less plausible
than those of the liquidity-trap type.
16. It should be noted that this argument regards the form of (least squares) learnability in question as a necessary,
not sufficient, condition for plausibility. In particular, it emphasizes that the relevant learning process assumes
that (1) agents collect an ever-increasing number of observations on all relevant variables while (2) the system’s
structure remains unchanged. Furthermore, (3) the agents estimate the relevant unknown parameters with anappropriate estimator in (4) a properly specified model. Thus, if a proposed RE solution is not learnable by theprocess in question, it would seem distinctly implausible that it could prevail in practice.
17. This conclusion is basically consistent with that of Woodford (2003, pp. 123–129), although the latter’s argument
is expressed rather differently.

23

APPENDIX: THE MODIFIED UIP EQUATION
Here we are concerned with the modified UIP equation (11′), which was introducedin Section IV. Note that (11′) is similar to equations prominent in several older
writings by Dornbusch (e.g., Dornbusch [1987, p. 7]) and others. These represented
a “portfolio balance” approach that was initially prominent but waned in influence asa result of empirical studies that failed to find empirical support. Nevertheless, it is,
I would argue, implausible to believe that no such relation obtains in fact, not evenwith weak or transitory effects of the Bt −BtF variable. Interestingly, models of this typehave quite recently been utilized by several leading researchers,18 while Mussa (2000)
has recognized that the absence of any effect of the type hypothesized—that is, theabsence of Bt − BtF—implies that a nation can enrich itself to an unlimited extent
by printing money and buying up foreign assets. The point is that if a relation suchas (11′) does prevail, then our simulation procedure in Section IV is theoreticallyappropriate, since (11′) indicates that even with R t = 0, st can be affected by central
bank purchases of foreign exchange because they alter the value of Bt − BtF.
Nevertheless, the precise specification of relation (11′) need not be known, and therelation need not be included in the model, for basically the same reason thatmoney demand functions are not needed in standard analyses which presume use of aninterest rate instrument. Thus, appending (11′) to the model would have no effect on
the implied behavior of pt , xt , yt , or st ; it would merely specify the magnitude ofopen market purchases of foreign exchange needed to implement the policy rule (13′).

References

Auerbach, A. J., and M. Obstfeld, “The Case for Open-Market Purchases in a Liquidity Trap,” NBER
Working Paper No. 9814, National Bureau of Economic Research, 2003.
———, “Monetary and Fiscal Remedies for Deflation,” American Economic Review, Papers andProceedings , 94 (2), 2004, pp. 71–79.
Baba, N., S. Nishioka, N. Oda, M. Shirakawa, K. Ueda, and H. Ugai, “Japan’s Deflation, Problems in
the Financial System, and Monetary Policy,” Monetary and Economic Studies, 23 (1), Institute for
Monetary and Economic Studies, Bank of Japan, 2005, pp. 47–111.
Ball, L., “Fiscal Remedies for Japan’s Slump,” NBER Working Paper No. 11374, National Bureau of
Economic Research, 2005.
Benhabib, J., S. Schmitt-Grohé, and M. Uribe, “The Perils of Taylor Rules,” Journal of Economic Theory ,96 (1–2), 2001, pp. 40–69.
———, ———, and ———, “Avoiding Liquidity Traps,” Journal of Political Economy , 110 (3), 2002,
pp. 535–563.
Bernanke, B. S., “Japanese Monetary Policy: A Case of Self-Induced Paralysis?” in R. Mikitani and A. S.
Posen, eds. Japan’s Financial Crisis and Its Parallels to U.S. Experience , Washington, D.C.:
Institute for International Economics, 2000.
———, and V. R. Reinhart, “Conducting Monetary Policy at Very Low Short-Term Interest Rates,”
American Economic Review, Papers and Proceedings , 94 (2), 2004, pp. 85–90.
———, ———, and B. P. Sack, “Monetary Policy Alternatives at the Zero Bound: An Empirical
Assessment,” Brookings Papers on Economic Activity , 2, 2004, pp. 1–78.
18. Essentially the same relation as (11′) has recently been central to the analyses of Flood and Marion (2000), Floodand Jeanne (2005), and Blanchard, Giavazzi, and Sa (2005). Microeconomic support is provided by Jeanne andRose (2002), and the prominent work of Evans and Lyons (e.g., Evans and Lyons [2002]) is indirectly supportive.

24 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006

Misconceptions Regarding the Zero Lower Bound on Interest Rates

Blanchard, O. J., F. Giavazzi, and F. Sa, “The U.S. Current Account and the Dollar,” NBER Working
Paper No. 11137, National Bureau of Economic Research, 2005.
Coenen, G., and V. Wieland, “The Zero-Interest-Rate Bound and the Role of the Exchange Rate for
Monetary Policy in Japan,” Journal of Monetary Economics, 50 (5), 2003, pp. 1071–1101.
Dornbusch, R., “Exchange Rate Economics: 1986,” Economic Journal , 97 (385), 1987, pp. 1–18.
Eggertsson, G. B., and M. Woodford, “The Zero Bound on Interest Rates and Optimal Monetary
Policy,” Brookings Papers on Economic Activity , 1, 2003, pp. 139–233.
———, and ———, “Policy Options in a Liquidity Trap,” American Economic Review, Papers andProceedings, 94 (2), 2004, pp. 76–79.
Evans, D. D., and R. K. Lyons, “Order Flow and Exchange Rate Dynamics,” Journal of Political Economy ,110 (1), 2002, pp. 170–180.
Evans, G. W., and S. Honkapohja, Learning and Expectations in Macroeconomics, Princeton: Princeton
University Press, 2001.
Flood, R. P., and N. P. Marion, “Self-Fulfilling Risk Predictions: An Application to Speculative Attacks,”
Journal of International Economics, 50 (1), 2000, pp. 245–268.
———, and O. Jeanne, “An Interest Rate Defense of a Fixed Exchange Rate?” Journal of International
Economics, 66 (2), 2005, pp. 471–484.
Fujiwara, I., N. Hara, N. Hirakata, S. Watanabe, and K. Yoshimura, “Monetary Policy in a Liquidity Trap:
What Have We Learned, and to What End?” International Finance, 8 (3), 2005, pp. 471–508.
Goodfriend, M. “Comments,” in I. Kuroda, ed. Towards More Effective Monetary Policy, London:
Macmillan Press in Association with the Bank of Japan, 1997.
———, “Overcoming the Zero Bound on Interest Rate Policy,” Journal of Money, Credit and Banking,32, November, 2000, pp. 1007–1035.
Iwamoto, Y., “Monetary and Fiscal Policy to Escape from a Deflationary Trap,” Monetary and Economic
Studies, 23 (1), Institute for Monetary and Economic Studies, Bank of Japan, 2005, pp. 1–46.
Jeanne, O., and A. K. Rose, “Noise Trading and Exchange Rate Regimes,” Quarterly Journal of Economics,
117 (2), 2002, pp. 537–569.
Jung, T., Y. Teranishi, and T. Watanabe, “Optimal Monetary Policy at the Zero-Interest-Rate Bound,”
Journal of Money, Credit and Banking, 37 (5), 2005, pp. 813–835.
Krugman, P., “It’s Baaack! Japan’s Slump and the Return of the Liquidity Trap,” Brookings Papers on
Economic Activity, 2, 1998, pp. 137–187.
Lucas, R. E., Jr., “Rules, Discretion, and the Role of the Economic Advisor,” in S. Fischer, ed. Rational
Expectations and Economic Policy , Chicago: University of Chicago Press, 1980.
McCallum, B. T., “Theoretical Analysis Regarding a Zero Lower Bound on Nominal Interest Rates,”
Journal of Money, Credit and Banking, 32 (4), 2000, pp. 870–904.
———, “Inflation Targeting and the Liquidity Trap,” in N. Loayza and R. Soto, eds. Inflation Targeting:
Design, Performance, Challenges, Central Bank of Chile, 2002.
———, “Japanese Monetary Policy, 1991–2001,” Economic Quarterly, 89 (1), Federal Reserve Bank ofRichmond, 2003, pp. 1–31.
———, “A Monetary Policy Rule for Automatic Prevention of a Liquidity Trap,” NBER Working Paper
No. 11056, National Bureau of Economic Research, 2005.
———, and E. Nelson, “Nominal Income Targeting in an Open-Economy Optimizing Model,”Journal of Monetary Economics, 43 (3), 1999, pp. 553–578.
Meltzer, A. H., “Comments: What More Can the Bank of Japan Do?” Monetary and Economic Studies,17 (3), Institute for Monetary and Economic Studies, Bank of Japan, 1999a, pp. 189–191.
———, “The Transmission Process,” in Deutsche Bundesbank, ed. The Monetary Transmission Process:
Recent Developments and Lessons for Europe, New York: Palgrave, 1999b.
Mussa, M., “Reflections on Monetary Policy at Low Inflation,” Journal of Money, Credit and Banking,32 (4), 2000, pp. 1100–1106.
Svensson, L. E. O., “The Zero Bound in an Open Economy: A Foolproof Way of Escaping from a
Liquidity Trap,” Monetary and Economic Studies, 19 (S-1), Institute for Monetary and Economic
Studies, Bank of Japan, 2001, pp. 277–312.

25

———, “Escaping from a Liquidity Trap and Deflation: The Foolproof Way and Others,” Journal of
Economic Perspectives, 17 (4), 2003, pp. 145–166.
———, “Comment,” Brookings Papers on Economic Activity, 2, 2004, pp. 84–93.
Taylor, J. B., “Policy Rules as a Means to a More Effective Monetary Policy,” in I. Kuroda, ed. Towards
More Effective Monetary Policy , London: Macmillan Press in association with the Bank of Japan,
1997, pp. 28–39.
Ueda, K., “The Bank of Japan’s Struggle with the Zero Lower Bound on Nominal Interest Rates:
Exercises in Expectations Management,” International Finance, 8 (2), 2005, pp. 329–350.
Woodford, M., Interest and Prices: Foundations of a Theory of Monetary Policy, Princeton: Princeton
University Press, 2003.

26 MONETARY AND ECONOMIC STUDIES (SPECIAL EDITION)/DECEMBER 2006