QE 1 vs. 2 vs. 3...

A Framework for Analyzing

Large Scale Asset Purchases as a

Monetary Policy Tool*

Mark Gertler and Peter Karadi

NYU and ECB

March 2012

Abstract

We introduce large scale asset purchases (LSAPs) as a monetary

policy tool within a macroeconomic model. We allow for purchases

of both long term government bonds and securities with some private

risks. We argue that LSAPs should be thought of as central bank

intermediation that can affect the economy to the extent there exist

limits to arbitrage in private intermediation. We then build a model

with limits to arbitrage in banking that vary countercyclically and

where the frictions are greater for private securities than for government bonds. We use the framework to study the impact of LSAPs

that have the broad features of the different QE programs the Fed

pursued over the course of the crisis. We find: (i) LSAPs work in the

model in a way mostly consistent with the evidence; (ii) purchases of

securities with some private risk have stronger effects than purchases

of government bonds; (iii) the effects of the LSAPs depend heavily on

whether the zero lower bound is binding. Our model does not rely

on the central bank having a more efficient intermediation technology

than the private sector: We assume the opposite. ∗ Prepared for the FRB Conference in honor of Don Kohn. Thanks

to Olivier Blanchard and V.V. Chari for helpful comments.

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1 Introduction

For the last fifty years or so, the primary tool of monetary policy has been the

Federal Funds rate. During the recent crisis, however, the Federal Reserve

unveiled a variety of new policy measures never used before in its history.

What forced its hand initially was the disruption of credit markets in the

wake of the deterioration of the subprime mortgage market, which began in

August of 2007. By December of 2008, however, a second factor came into

play: The Funds rate effectively reached its zero lower bound, implying that,

despite the severity of the recession, the conventional option of reducing the

Funds rate was no longer available. Beyond managing expectations of the

future path of the Funds rate, the new unconventional measures afforded the

Fed the only avenue for stimulating the economy.

Because of their dramatic impact on the size of the Fed’s balance sheet,

the most visible of the new policy measures have been large asset scale purchases (LSAPs), known more generally as quantitative easing (QE). Shortly

after the meltdown of the shadow banking system that followed the Lehman

failure in September 2008, the Fed initiated what is now known as QE1:

the purchase over time of a variety of high grade securities, including agency

mortgage backed securities (AMBS), agency debt, and long term government

bonds, with AMBS ultimately accounting for the bulk of the purchases. It

also set up a commercial paper lending facility, which effectively involved

the purchase of commercial paper since the Fed accepted these instruments

as collateral for the loans made to the facility. In October 2010, the Fed

announced a second wave of asset purchases (QE2), this time restricted to

long term government bonds and smaller in scale than QE1. Finally, in September 2011, the Fed embarked on a variation of QE, known as Operation

Twist. This action was essentially a sterilized acquisition of long term government bonds financed by selling some of its short term bonds. Twist was

extended in the summer of 2012 and the possibility of more LSAPs remains

under discussion.

A lengthy empirical literature has emerged attempting to identify the

effects of the LSAP programs on market interest rates and economic activity1. Though not without considerable controversy, a common theme of this

1See, for example, Baumeister and Benati (2010), Chung et.al. (2011), D’Amico and

King (2010), Doh(2010), Gagnon, Raskin, Remache and Sack (2011), Gambacorta, Hoffman, and Peersman (2011), Hamilton and Wu (2010), Hancock and Passmore (2011) Krishmamurthy and Vissing-Jorgensen (2011), Stroebel and Taylor (2009), Williams (2011)

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research is that the LSAPs have indeed been effective in reducing various

interest rates and interest rate spreads and, as a consequence, in stimulating

economic activity. In addition, the weight of the evidence also suggests that

QE1 was more effective in this regard than either QE2 or Operation Twist.

At the same time, given the descriptive nature of much of this empirical work, the precise mechanism through which LSAPs may have affected

the economy remains an open question. So too is a theoretical account for

why QE1 may have had different effects than than the subsequent LSAP

programs. In addition, to being larger in scale, QE1 differed from the other

LSAPs in several other important respects. First, the asset purchases involved securities with at least some degree of private payoff risk, whereas

QE2 and Operation Twist were restricted to the acquisition of government

bonds. In addition, QE1 was undertaken at the height of the crisis when

financial markets and institutions were under maximum duress. By contrast,

QE2 and Operation Twist were undertaken in periods of greater normalization of credit markets. Exactly which of these factors could account for

differences in the impact of various LSAP programs has yet to be resolved.

The purpose of this paper is to develop a macroeconomic model that

presents a unified approach to analyzing LSAPs as a monetary policy tool. A

number of papers have analyzed specific types of LSAPs. For example Gertler

and Karadi (2011), Curdia and Woodford (2011), Del Negro, Eggertsson,

Ferrero and Kiyotaki (2011) and Williamson (2012) have considered central

bank purchases of imperfectly secured private claims, as in QE1. Others

have considered purchases of long term government bonds, such as Vayanos

and Vila (2009) and Chen, Curdia, and Ferrero (2011). The mechanisms

emphasized both within and across these strands of work have been somewhat

different. Our goal is to present a single framework that can be used to

analyze the impact of LSAPs across the variety that are used in practice.

As in Gertler and Karadi (2011; GKa) and Gertler and Kiyotaki (2011;

GKi), we start from the perspective that LSAPs reflect central bank intermediation. Like any private intermediary, the central bank funds asset acquisition by issuing interest bearing short term claims. In the early stages of QE1

the Fed raised funds by issuing short term government debt it borrowed from

the Treasury. Shortly thereafter, it made use of its recently acquired power to

pay interest on reserves. It funded subsequent expansion of its balance sheet

by issuing interest bearing reserves, which can be thought of as overnight

and Wright (2011).

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government debt. Seen from this vantage, it is clear that LSAPs can usefully

affect real activity only to the extent there exist limits to arbitrage in private financial intermediation. If an extranormal return on a particular asset

is present, one would expect private intermediaries to expand their balance

sheets to eliminate this premium, so long as they do not face any constraints

in borrowing. In this instance, as we will make clear, central bank intermediation of the asset is neutral: It does not affect asset prices and returns: It

simply displaces private intermediation.

If however private intermediaries are constrained in their ability to borrow, LSAPs can matter. The advantage the central bank has is that it is

able to obtain funds elastically by issuing riskless government debt. It is this

advantage in borrowing over private intermediaries that introduce a role for

central bank intermediation in reducing excess returns. In this regard, as

GKa show, the net benefits from LSAPs can be positive even if the central

bank is less efficient than the private sector in intermediating the assets, so

long as this efficiency differential is not "too large." Further, these net benefits are likely to be increasing in a financial crisis since in this instance limits

to private arbitrage are likely to be unusually tight.

Along these lines, one can interpret QE1 as the Federal Reserve increasing

central bank intermediation to offset the disruption of private intermediation

brought about by the demise of the shadow banking system.2 Indeed, the

assets it purchased were held largely by the financial institutions that had

devolved into distress. Further, given that various measures of credit spreads

suggested that excess returns were at a peak in the wake of the Lehman

collapse, the expected gains from central bank intermediation were likely

largest at this point. It is this kind of reasoning about the effect of QE1 that

our model will capture.

We will also argue that a similar logic applies to the purchase of long

term government bonds. Absent limits to arbitrage in the private sector,

central bank exchanges of short term for long term government debt should

be neutral. To the extent that credit market frictions give rise to an extranormal term premium in the market for government bonds, there is scope for

LSAPs to reduce long term rates.3 The way they reduce long term rates is by

2Here it is interesting to note that Ben Bernanke used the term "credit easing" to

describe the first round of LSAPs. We think this is a more accurate term than quantitative

easing. See, for example, Bernanke (2009)

3For financial institutions borrowing from the Fed using ten year government bonds as

collateral, there is a four percent haircut. One would expect that private lenders require

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reducing inefficiently large term premia. Of course, one should expect limits

to arbitrage to be weaker in markets for government bonds than for private

securities. We incorporate this feature in our model. The net effect is that

a dollar purchase of government bonds has a weaker effect on excess returns

than a dollar purchase of private sector assets. This accords with the conventional wisdom that the liquidity of the government bond market makes

purchases of this asset less effective everything else equal than purchases of

less liquid assets such as AMBS or commercial paper.

An alternative view of how LSAPs affect the economy stresses household

asset demands that are less sensitive to returns than a standard frictionless model might predict, due to factors such as a "preferred habitat" for

particular maturities.4 Given these frictions in asset demand, changes in

asset supplies in the private sector brought about by LSAPs affect prices

and returns of competing assets. What matters however is the behavior of

the marginal investors, which in reality are likely to be leveraged financial

intermediaries.

Indeed, as Table 1 shows, in 2008 leveraged financial institutions held significant fractions of the types of assets ultimately acquired under the various

LSAP programs, including roughly forty-five percent of the AMBS outstanding, forty percent of the agency debt, and sixteen percent of the government

debt.5 Thus, any characterization of how LSAPs affect the economy must

take into account the behavior of these institutions. In this respect, even

if household demands for long maturity assets are "excessively inelastic",

arbitrage by private intermediaries could render central bank purchases of

long term government bonds neutral. We clarify this point within our formal

analysis.

Section 2 presents the key elements of our model. We derive a set of qualitative results regarding how LSAPs affect the economy. Section 3 adds the

production sector and then characterizes the complete equilibrium. Section 4

then presents some numerical experiments to illustrate the impact of LSAPs.

Here we emphasize the implications of purchases of securities with private

risks versus long term government bonds. We also consider the implications

of the zero lower bound and also compare LSAPs with conventional interest

a larger haircut on these bonds, suggesting at least some degree of friction in the market.

4See for example Chen, Curdia and Ferrero (2011) and the references there-in.

5Following Greenlaw, Hatzius, Kashyap and Shin (2008), we define leveraged institutions as those intermediaries whose equity capital is only a small fraction of the assets

they hold and whose liabilities consist mostly of short term debt.

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rate adjustments. Concluding remarks are in section 6.

2 The Model: Key Ingredients

The framework is based on GKa. It is a reasonably standard New-Keynesian

model modified to allow for banks that transfer funds from households to nonfinancial firms, as well as to the government. An agency problem constrains

the ability of banks to obtain funds from households. It ultimately makes

the balance sheet of the banking sector a critical determinant of the cost

of credit that borrowers face. One difference from GKa is that banks may

intermediate the funding of long term government bonds as well the funding

of non-financial firms.

In addition, there is a central bank that can conduct monetary policy

either by adjusting the short term interest rate (so long as the zero lower

bound is not binding) or by engaging in asset purchases. The central bank

may purchase long term government bonds as well as private securities.

In this section we characterize the distinctive elements of the model, which

involve the behavior of households, banks and the central bank. We defer

a description of the production sector and complete equilibrium to the next

section. For didactic reasons, we start with the case where banks intermediate

all the funding of non-financial firms and long-term government bonds. This

simple setup allows us to starkly illustrate some of key results regarding

the effects of central bank asset purchases. We then subsequently allow

households to directly hold long term securities subject to transactions costs

and then draw out the implications of this more general setting.

In the interest of parsimony, we abstract from a number of the features

present in conventional quantitative DSGE models that are not central to

understanding the effects of central bank asset purchases (e.g, variable capital utilization, wage rigidity, price and wage indexation, etc.). However we

include two standard features, habit formation and flow investment adjustment, because they can be added at minimal cost of complexity and they

substantially improve the model’s quantitative performance.

Finally, we should make clear that we do not attempt to develop a model

that can provide a comprehensive description of recent events. We do not

include an explicit housing sector nor do we try to model asset bubbles, etc.

Rather our goal is to formulate a macroeconomic model to help understand

how LSAPs might work in a setting that has some of the key features of the

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current crisis.

2.1 Households

There is a continuum of identical households of measure unity. Each household consumes, saves and supplies labor. Households save by lending funds

to competitive financial intermediaries and possibly also by lending funds to

the central bank.

Within each household there are two types of members: workers and

bankers. Workers supply labor and return the wages they earn to the household. Each banker manages a financial intermediary and similarly transfers

any earnings back to the household. The household thus effectively owns the

intermediaries that its bankers manage. It deposits funds, however, in intermediaries that is does not own. Finally, within the family there is perfect

consumption insurance. As will become clear, this simple form of heterogeneity within the family allows us to introduce financial intermediation in a way

that maintains much of the tractability of a representative agent framework.

At any moment in time the fraction 1 −  of the household members

are workers and the fraction  are bankers. Over time an individual can

switch between the two occupations. In particular, a banker this period stays

a banker next period with probability  which is independent of history.

The average survival time for a banker in any given period is thus 1

1−  We

introduce a finite horizon for bankers to insure that over time they do not

retain earnings to the point where they can fund all investments from their

own capital. Thus every period (1 − ) bankers exit and pay out their

retained earnings as dividends to their respective household. The bankers

who exit become workers and are replaced by a similar number of workers

randomly becoming bankers, keeping the relative proportion of each type

fixed. The household, though, provides its new bankers with a small amount

of start up funds equal to 

(1−) per new banker.

Let  be consumption and  family labor supply. Then the households

discounted utility  is given by

 = 

X∞

=0



∙

ln(+ − +−1) − 

1 + 

1+

+

 ̧

(1)

with 0  1 0  1 and    0. As in Woodford (2003), we

consider the limit of the economy as it become cashless, and thus ignore the

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convenience yield to the household from real money balances.

Both intermediary deposits and government debt are one period real

bonds that pay the gross real return  from −1 to  In the equilibrium we

consider, the instruments are both riskless and are thus perfect substitutes.

Thus, we impose this condition from the outset. Thus let  be the total

quantity of short term debt the household acquires, , be the real wage, Π

payouts to the household from ownership of both non-financial and financial

firms and,  lump sum taxes. Then the household budget constraint is given

by

 =  + Π −  +  + −1 −  (2)

where  is the total transfer the household gives to its members that enter

banking at . Finally, as will be clear later, it will not matter in our model

whether households hold government debt directly or do so indirectly via

financial intermediaries (that in turn issue deposits to households.)

The household’s objective is to choose   and  to maximize (1)

subject to (2). Let  denote the marginal utility of consumption. Then the

first order conditions for labor supply and consumption/saving are standard:

 = 

 (3)

Λ+1+1 = 1 (4)

with

Λ+1 ≡  +1



2.2 Banks

Banks lend funds obtained from households to non-financial firms and to

the government. In addition to acting as specialists that assist in channeling

funds from savers to investors, they engage in maturity transformation. They

hold long term assets and fund these assets with short term liabilities (beyond

their own equity capital.)6 In addition, financial intermediaries in this model

6 In Gertler and Kiyotaki (2011), we consider a generalization of this framework that

has banks manage liquidity risks (stemming from idiosyncratic shocks to firm investment

opportunities) via an interbank market. In this setup, financial frictions may also affect

the functioning of the interbank market.

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are meant to capture the entire banking sector, i.e. investment banks as well

as commercial banks.

Intermediaries fund two type of activities: First, they make loans to nonfinancial firms to finance capital. Let  be the net period income flow to

the bank from a loan that is financing a unit of capital, , the market value

of the security,  the depreciation rate of a unit of capital and  a random

disturbance. Then the rate of return to the bank on the loan, +1, is given

by:

+1 = +1 + (1 − )+1



+1 (5)

The variables   , and  are determined in the general equilibrium of the

model, as we show later.

In addition, banks hold long term government bonds. Here we suppose

that it is too costly for households to directly manage long term bonds in

their portfolios. As we noted earlier, we relax this assumption by permitting

household to directly hold long term securities subject to explicit transactions

costs. For our benchmark model, however, banks intermediate all the funding

of long term bonds. We assume each bond is a perpetuity that pays one dollar

per period indefinitely. Let  be the price of the bond and  the price level.

Then the real rate of return on the bond +1 is given by

+1 = 1 + +1



(6)

The general equilibrium also determines  and 

2.2.1 The Bank’s Maximization Problem

Let  be the amount of equity capital - or net worth - that a banker/intermediary

 has at the end of period ;  the deposits the intermediary obtains from

households,  the quantity of financial claims on non-financial firms that the

intermediary holds and  the quantity of long term government bonds. The

intermediary balance sheet is then given by

 +  =  +  (7)

Net worth is accumulated through retained earnings. It is thus the difference

between the gross return on assets and the cost of liabilities:

 = −1−1 + −1−1 − −1 (8)

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The banker’s objective is to maximize the discounted stream of payouts

back to the household, where the relevant discount rate is the household’s

intertemporal marginal rate of substitution, Λ+ Under frictionless capital

markets the timing of the payouts is irrelevant. To the extent the intermediary faces financial market frictions, it is optimal for the banker to retain

earnings until exiting the industry. Accordingly, the banker’s objective is to

maximize expected terminal wealth, given by

 = 

X∞

=1

(1 − )−1Λ++ (9)

To motivate a limit on the bank’s ability to obtain deposits, we introduce

the following moral hazard/costly enforcement problem: At the beginning

of the period the banker can choose to divert funds from the assets it holds

and transfer the proceeds to the household of which he or she is a member.7

The cost to the banker is that the depositors can force the intermediary into

bankruptcy and recover the remaining fraction of assets. However, it is too

costly for the depositors recover the funds that the banker diverted.

We assume that it is easier for the bank to divert funds from its holdings

of private loans than from its holding of government bonds: In particular,

it can divert the fraction  of its private loan portfolio and the fraction ∆

with 0 ≤ ∆  1 from it government bond portfolio. Here we are attempting

to capture in a simple way that the bank’s private loan portfolio is likely an

easier target for bank malfeasance than its government bond portfolio given

that it is more difficult for depositors to monitor the performance of latter

than the former.8

Accordingly for depositors to be willing to supply funds to the banker,

the following incentive constraint must be satisfied

 ≥  + ∆ (10)

The left side is what the banker would lose by diverting a fraction of assets.

The right side is the gain from doing so.

7One way the banker may divert assets is to pay out large bonuses and dividends to

the household.

8A more explicit approach to motivating weaker limits to arbitrage for long term government bonds would be to allow for default risk on private securities in a way that

enhances the agency friction. For parsimony, we stick with our simple friction as a way to

motivate differential arbitrage limits (stemming from balance sheet constraints.)

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The bankers maximization problem is to choose   and  to maximize

(9 ) subject to (7), (8) (10).

2.2.2 Solution

Let  be the Lagrange multiplier associated with the incentive constraint

(10) and let Λe+1 be the bank’s "augmented" stochastic discount factor,

equal to the product Λ+ and the multiplier Ω+1:

Λe+1 ≡ Λ+1 · Ω+1 (11)

where the Ω+1 reflects the shadow value of a unit of net worth to the bank

at  + 1, as we make clear shortly. Then we can characterize the solution as

follows:

The expected excess returns on bank assets satisfy9

Λe+1(+1 − +1) = 

1 + 

 (12)

Λe+1(+1 − +1) = ∆ · 

1 + 

 (13)

When the incentive constraint is not binding the discounted excess returns are zero. With  = 0, ∀ ,financial markets are frictionless: Banks

acquire assets to the point where the discounted return on each asset, equals

the discounted cost of deposits. Further, in this case Ω+1 equals unity, so

that for each asset the standard arbitrage condition under perfect markets

arises: The expected product of the households’ intertemporal marginal rate

of substitution and the excess return equals zero.

When the incentive constraint is binding, however, limits to arbitrage

emerge that lead to positive excess returns in equilibrium. The excess returns

increase with how tightly the incentive constraint binds, as measured by the

multiplier . Note that the excess return to capital implies that for a given

riskless interest rate, the cost of capital is higher than would otherwise be.

As consequence, investment and real activity will be lower than would be

9Here we use the term excess return to refer to the difference between the discounted

return and what its value would be under frictionless markets. This is different from

the standard use in finance, where the term reflects the premium due to risk (within a

frictionless market setup.)

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otherwise in general equilibrium. Indeed, a financial crisis in the model will

involve a sharp increase in the excess return to capital.

Notice also that the excess return on government bonds is smaller than

the excess return on loans by the multiple ∆  1 This occurs because the

proportion of funds a bank can divert from its bond portfolio is only the

fraction ∆ of the proportion it can divert from its loan portfolio. As a result

the incentive friction that limits arbitrage is weaker for government bonds

than for loans by the factor ∆

The limits to arbitrage stem from the following restriction that the incentive constraint places on the size of a bank’s portfolio relative to its net

worth:

 + ∆ =  if   0; (14)

  if  = 0

with

 = Λe+1+1

 − Λe+1(+1 − +1) (15)

The measure of assets that enters the bank’s balance sheet constraint applies a weight of ∆ to government bonds, reflecting the weaker constraint on

arbitrage for this asset than for loans. As the bank expands this adjusted

measure of assets by issuing deposits, its’ incentive to divert funds increases.

The constraint (14) limits the portfolio size to the point where the bank’s

incentive to cheat is exactly balanced by the cost of losing the franchise value.

In this respect the agency problem leads to an endogenous capital constraint.

Observe that  is the maximum ratio of the adjusted measure of assets to

net worth that the bank may hold without violating the incentive constraint.

It depends inversely on ; An increase in the bank’s incentive to divert funds

reduces the amount depositors are willing to lend. Conversely, an increase

in the discounted excess return on assets, Λe+1(+1 − +1) or the

discounted safe rate, Λe+1+1increases the franchise value of the bank,

 reducing the bank’s incentive to divert funds. Depositors thus become

willing to lend more, raising 

Finally, the weight Ω+1 that augments the bank’s discount factor is the

marginal value of net worth averaged across exiting and continuing states:

Ω+1 = 1 −  + 

+1

+1

(16)

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with





= Λe+1[(+1 − +1) + +1]

With probability 1 −  the bank exits and has a marginal value of net worth

of unity since it simply transfers its retained earnings to the household. With

probability  it continues and uses the net worth to expand its base asset

base. So long as the excess returns on assets are positive, the marginal value



 exceeds unity.

2.2.3 Aggregation

Let  be the total quantity of loans that banks intermediate,  the total

number of government bonds they hold. and  their total net worth. Since

neither component of the maximum adjusted leverage ratio  depends on

bank specific factors, we can simply sum across the portfolio restriction on

each individual bank (14) to obtain

 + ∆ ≤  (17)

Equation (17) restricts the aggregate value of (adjusted) assets that the banking system can hold to be less than or equal to the multiple  of total bank

capital. When the constraint is binding, variation in  will induce fluctuations in overall asset demand by intermediaries. Indeed, in the general

equilibrium of the model, a crisis will feature a sharp contraction in 

Total net worth evolves as the sum of the retained earnings by the fraction

 of surviving bankers and the transfers that new bankers receive, , as

follows.

 = [( − )

−1−1

−1

+ ( − )

−1−1

−1

+ ]−1 +  (18)

The main sources of variation in  are fluctuations in the ex post return

on loans  and the ex post return on bonds . Further, the percentage

impact of this return variation on  in each case, is increasing in the bank’s

degree of leverage, reflected by the respective ratios of assets to net worth,

−1−1−1 and −1−1−1

13
2.3 Central Bank Asset Purchases

As equations (12) and (13) suggest, if private intermediation is balance sheet

constrained, excess returns on assets arise. If these constraints are particularly tight, as would be the case in a financial crisis, then excess returns will

be unusually high, with negative consequences for the cost of capital and real

activity. Within our model, large scale asset purchases provide a way for the

central bank to reduce excess returns and thus mitigate the consequences of

a disruption of private intermediation.10

In particular, we now allow the central bank to purchase quantities private loans  and long term government bonds   For each each type of

security it pays the respective market prices  and  Though when limits

to arbitrage in the private market are operative, the central bank’s acquisition of securities will have the effect of bidding up the prices on each of

these instruments and down the excess returns. To finance these purchases,

it issues riskless short term debt  that pays the safe market interest rate

+1 In particular, the central bank’s balance sheet is given by

 +  =  (19)

where we assume that the central bank turns over any profits to the Treasury

and receives transfers to cover any losses. For the time being we suppose that

the central bank issues the short term debt to households. Later we discuss

an equivalent scenario where  is interpretable as interest bearing reserves

(essentially overnight government debt) held by banks on account at the

central bank.

As we discussed earlier, these kinds of asset purchases essentially involve

substituting central bank intermediation for private intermediation. What

gives the central bank an advantage in this situation is that, unlike private

intermediaries it is able to obtain funds elastically by issuing short term

liabilities. It is able to do so because within our framework the government

can always commit credibly to honoring its debt. Accordingly, there is no

10We abstract from moral hazard considerations emphasized, for example, by Chari and

Kehoe (2010) and Farhi and Tirole (2012). Gertler, Kiyotaki and Queralto (2011) address

this issue in a framework similar to the one here by allowing banks the options of issuing

outside equity as well as deposits, where equity issuance is subject to agency costs. The

possibility of LSAPs then reduces banks’ incentives to hedge their portfolios. The precise

degree is a quantitative issue. We would expect a similar outcome in the framework here

but defer an explicit treatment to future.

14
agency conflict than inhibits the central bank from obtaining funds from the

private sector. Put differently, in contrast to private financial intermediation,

central bank intermediation is not balance sheet constrained.11

At the same time, we allow for the central bank being less efficient than

the private sector at making loans. In particular, we assume the central bank

pays an efficiency cost of   per unit of private loans intermediated and  

per unit of government bonds. Accordingly, for asset purchases to produce

welfare gains, the central bank’s advantage in obtaining funds cannot be

offset by its disadvantage in making loans. Its advantage in obtaining funds

is greatest when excess returns are large (i.e when limits to private arbitrage

are tight), as will be the case in a financial crises. As for its disadvantage

in making loans: It is reasonable to suppose the relative efficiency cost of

intermediating government bonds,   is small. For  , it depends on the type

of credit instrument. The types of "private loans" for which one might expect

  to be small include highly rated securitized assets such as agency mortgage

backed securities as opposed to commercial and industrial loans that involve

extensive monitoring. Accordingly, it is the former type of instrument we

have in mind in characterizing central bank purchases of private securities as

opposed to the latter.

The way asset purchases affect the real economy is ultimately by affecting

the price  and (hence the) excess return on capital Λe+1(+1 −+1)

Accordingly, let  and  be the total supplies of private loans and long

term government bonds, respectively. Then by definition:

 =  +  (20)

 =  + 

where as before  and  are the total amounts that are privately intermediated. We combine these identities with the balance constraint on the banks

to obtain the following relation for total the total value of private securities

intermediated,  :

 ≤  +  + ∆( − ) (21)

11As Wallace (1981) originally noted, for government financial policy to matter it is important to identify what is special about government intermediation. Sargent and Wallace

(1981) provide an early example of how credit policy could matter, based on a setting of

limited participation in credit markets.

15
When the aggregate balance sheet constraint is not binding, asset prices

and returns are determined by frictionless arbitrage. Asset purchases by the

central bank of either private loans or long term bonds are neutral. They

simply lead to central bank intermediation displacing some private intermediation, without any effect on asset prices. To the extent central bank

intermediation involves efficiency costs, further, asset purchases are clearly

welfare reducing in this kind of environment.

This neutrality result disappears, however, if the constraint is binding.

Given the total quantity of bank equity, an increase in the central bank’s

holding of either private securities or long term governments raises the total

demand for private securities. Intuitively, with limits to arbitrage present

on private credit flows, central bank intermediation expands overall asset

demand and does not simply displace bank intermediation one for one. Further, given that asset supplies are relatively inelastic in the short run, the

enhanced asset demand pushes up  and down the excess return on capital.

Equation (21) also reveals that it matters which asset the central bank

acquires. In particular, purchases of government bonds will have a weaker

effect on the demand for private assets than would the the direct purchase of

this asset by the factor ∆  1 Intuitively, the central bank acquiring government bonds frees up less bank capital than does the does the acquisition of

a similar amount of private loans. It is effectively by freeing up intermediary

capital that asset purchases are able to expand the overall demand for private

assets. In the limiting case of frictionless arbitrage in the government bond

market (i.e., ∆ = 0), bond purchases have no effect.

Purchases of either asset affect the excess returns of both due to the

arbitrage relation implied by equations (12) and (13):

Λe+1(+1 − +1) = ∆Λe+1(+1 − +1) (22)

As we noted earlier, though, because limits to arbitrage are weaker for government bonds than for private securities, the excess return on the former

is only the fraction ∆ of the excess return on the latter. Thus, everything

else equal, in the wake of an asset purchase, government bond yields should

move by less than the yield on private securities. This should hold regardless

of which asset the central bank purchases.

Finally, up to this point we have assumed that the central bank funds

assets purchases by issuing short term debt directly to households. An equivalent formulation has the central bank issue the debt directly banks which

16
in turn fund this activity by issuing deposits to households. The short term

government debt that banks absorb, further, can take the form of interest

bearing reserves held on account at the central bank, as was the case in practice for the most part. Assuming that the agency friction does not apply to

intermediating reserves, the bank will not be constrained in its funding of this

asset. Thus, as in the baseline scenario, the central bank is able to elastically

issue short term liabilities to fund its asset purchases. It is straightforward

to show that the equilibrium conditions in the scenario are identical to those

in the baseline case. The identical balance sheet constraint on bank asset

holdings applies.

Along these lines, it does not matter whether the central bank finances

asset purchases by issuing short term liabilities or by selling some of its

holdings of short term government debt, so long as its short term assets and

liabilities are in effect perfect substitutes. Thus for example, purchases of long

term government bonds financed by interest bearing reserves, as occurred

under QE2, are equivalent to purchases financed by selling holdings of short

term Treasury Bills, so long the Treasury Bills and interest bearing reserves

are close substitutes. In either case, the central bank is expanding the amount

of long term government bonds funded by short term debt government debt.

Also, how the asset purchase works in either case depends on the same set

of considerations: the extent of limits to arbitrage in private markets.

2.4 Allowing for Direct Household Securities Holdings

We now permit households to directly hold private securities and long term

government bonds. However, we introduce limits on household participation

by assuming transaction costs. Absent these costs, households would engage

in frictionless arbitrage of asset returns.

We suppose that for private securities a household faces a holding cost

equal to the percentage 1

2( −)2 of the value of the securities in its

respective portfolio for  ≥ . Similarly, for government bonds there is a

holding cost equal to the percentage 1

2( − )2 of the total value of

government bonds held for  ≥  Accordingly, there is a certain amount

of each asset that the household can hold costlessly. Going above these levels

involves transactions costs which are increasing at the margin. We motivate

this cost structure as capturing in a simple way limited participation in asset

markets by households that leads to incomplete arbitrage.

17
Accordingly, the household budget constraint becomes

 +  + [ +

1

2

( − )

2

] + [ +

1

2

( − )

2

]

=  + Π +  + −1 + −1 + −1

Resolving the household’s optimization yields the same first order conditions for labor supply and deposits as before. The choices for private securities and long term government bonds are given by

 =  +

Λ+1(+1 − +1)

 (23)

 =  +

Λ+1(+1 − +1)



Demand for each asset above its frictionless capacity level is increasing in

the excess return relative to the respective curvature parameter that governs

the marginal transaction cost. Note that as marginal transactions cost go to

zero, excess returns disappear: Households are able to engage is frictionless

arbitrage of security returns. Conversely, as marginal transactions costs go to

infinity, households asset demands go to their respective frictionless capacity

values,  and 

Overall, one can view the household asset demand structure as a parsimonious way to capture two important forms of heterogeneity that are absent

from the model. First, in reality, a sizeable fraction of non-financial firms

are able to obtain funds by issuing securities directly to households on the

open market and do not have to borrow directly from banks. These firms are

typically large well established entities, in contrast to younger and smaller

non-financial borrowers that typically require the kind evaluation and monitoring services that banks offer. Second, households differ in their ability to

manage a sophisticated portfolio: A limited supply of "sophisticated" households accordingly prevents frictionless arbitrage of security returns by the

household sector. In practice both forms of heterogeneity help explain why

both private and government securities holdings are divided between households and banks. Our model provides a very simple way to account for this

pattern of asset holdings that is meant to be a stand-in for a more explicit

treatment.

With households directly participating in securities markets, the equilibrium conditions in the markets for private loans and government bonds now

require:

18
 =  +  +  (24)

 =  +  + 

To understand the implications for central bank asset purchases, note that

with direct household participation in securities markets we can rewrite the

aggregate bank portfolio constraint (21) as

( − ) ≤  +  + ∆[ − ( − )] (25)

with  and  given by (23). The portfolio constraint is now a restriction

on the total demand for securities net the quantity held by households.

In this general case, the effects of asset purchases on prices and excess

returns depend on the responsiveness of household as well as bank portfolios

to arbitrage opportunities. Consider first the case where the the marginal

transaction costs facing the household are infinity (i.e.  = ∞). In this

instance, a household holds the respective frictionless capacity value of each

asset,  and  and is completely unresponsive to arbitrage opportunities.

Here the analysis is very similar to the simple case of no direct household

participation analyzed in section 2.2. If the portfolio constraint on banks is

not binding, then as before banks adjust their asset holding to drive excess

returns to zero. Even though households cannot absorb additional securities,

they are willing to absorb deposits which do not involve transactions costs.

Given that banks are free to arbitrage returns, central bank asset purchases

are neutral. An increase in either  or  simply leads to a one for one

reduction in private bank intermediation of the respective security without

any impact on prices or returns.

If the portfolio constraint binds then, as in the simple case of section 2.2,

asset purchases increase the net demand for private securities. The presence

of inelastic household security demands, further strengthens the effects of a

given size purchase of either security. It does so by reducing the participation of the active traders in the market (in this case the banks). Because

everything else equal the purchases are larger relative to bank holdings of

the respective asset, they will have a larger impact on prices and returns.

These results are consistent with the fact that asset prices depend on asset

supplies if household demand is relatively inelastic (e.g for "preferred habitat" reasons.) We stress, however, that it is also key that arbitrage by the

active traders in the market is limited. Absent the balance sheet constraint

19
on banks, asset purchases would be neutral despite inelastic asset demands

by households.

As household security demands become increasingly elastic ( moves toward zero), the effects of central bank asset purchases weaken. As before,

assuming total supplies of each asset are inelastic in the short run, central

bank purchases of either security will place downward pressure on excess

returns. A decline in excess returns, however, reduces households’ security

holdings, dampening the overall effect of the purchases on asset demands.

Put differently, household asset demands move in a way that offsets the effect of central bank asset purchases. This offsetting effect becomes stronger

as transactions cost become smaller. In the limiting case of zero transactions

cost, of course, households are able to perfectly arbitrage and central bank

asset purchases are neutral.

In sum, for central bank asset purchase to affect asset prices and returns,

limits to arbitrage must be present for both households and banks.

2.5 Long Term Bond Yields

We have argued that the effects of LSAPs are transmitted to the real economy

via their impact on excess returns (relative to a frictionless benchmark.)

Popular discussions of LSAPs, however, emphasize the impact on long term

bonds rates and various credit spreads. The empirical literature has followed

this direction by studying the effects of LSAPs on these variables. Of course

another relevant consideration in focusing on the behavior of these yields is

that excess returns are not directly observable.

Within our model the government bond is a consol that pays a dollar in

perpetuity. Let 

+1+ ≡ +1+ · +1+

+ be the ex post gross nominal return

on this security from  +1+ ; Then we can express the nominal price 

as the following discounted sum:

 = X∞

=1

1

Π

=1

+

(26)

To understand the impact of LSAPs on long term bond yields it is useful to

define ∗

+ as the ratio of nominal return in the absence of credit market

frictions, everything else equal; and define Ψ+ = 

+∗+ as the ratio

of nominal return to is "frictionless value". We can express the discounted

20
return as

 = X∞

=1

1

Π

=1Ψ+∗

+

(27)

where discount factors depend on the expected sequence of excess returns

measure by Ψ+  Finally, we compute the nominal (net) yield to maturity,

as the constant per period nominal discount rate 



 that yields the same

nominal value as the consol, given the same sequence of coupon payments:

X∞

=1

1

(1 + 



) = X∞

=1

1

Π

=1Ψ+∗

+

(28)

To a first order, we can decompose the movement in 



 into terms reflecting the expected path the frictionless nominal rate ∗

+ and terms reflecting

the excess return Ψ+  As we saw in the previous section, LSAPs work by

pushing down the component of 



 due to expected excess returns that stem

from limits to arbitrage. Absent these excess returns, LSAPs would have no

effect on 





On the other hand, to the extent that long term bond purchases are

successful in pushing down excess returns the overall impact on 



 may be

muted by an expected increase in the frictionless nominal rate. In particular,

by pushing down excess returns the LSAPs stimulate both real activity and

inflation, leading to an expected future increase in short term interest rates.

It is the expected response of future short rates than dampens the overall

responds of LSAPs on long term yields.

We can similarly construct a yield to maturity for the private security.

The main difference is that now the per period payoff is the nominal dividend

payment net depreciation, [+1 − ] +1 Finally, much of the evidence of

LSAPs on returns is reported for securities of a given finite maturity, as

opposed to consols or other kinds of infinitely-lived assets. In the quantitative

section we describe how we approximate the returns on shorter maturity

securities.

3 The Production Sector, Government, and

Equilibrium

We now close the model by describing the non-financial production sector,

government policy, and the general equilibrium.

21
3.1 Non-financial Firms

There are three types of non-financial firms in the model: intermediate goods

producers, capital producers, and monopolistically competitive retailers. The

latter are in the model only to introduce nominal price rigidities. We describe

each in turn.

3.1.1 Intermediate Goods Producers

Intermediate goods producers make output that they sell to retailers. They

are competitive and earn zero profits in equilibrium. Each operates a constant

returns to scale technology with capital and labor inputs. Let  be output,

 total factor productivity,  labor,  capital, Then:

 = 

 1−  (29)

Let  be the relative price of intermediate goods. Then the firm’s demand

for labor is given by

 = (1 − )





(30)

It follows that we may express gross profits per unit of capital  as follows:

 = 





 (31)

The acquisition of capital works as follows. At the end of any period ,

the intermediate goods producer is left with a capital stock of (1 − ). It

then buys  units of new capital from capital producers. Its capital stock

for  + 1 is then given by

+1 = +1[ + (1 − )] (32)

where  is a random disturbance that we refer to as a "capital quality"

shock. Following the finance literature (e.g., Merton (1973)), we introduce

the capital quality shock as a simple way to introduce an exogenous source

of variation in the return to capital12. It is best thought of as capturing some

12Other recent papers that make use of this kind of disturbance include, Gertler and

Karadi (2011), Brunnermeier and Sannikov (2009) and Gourio (2012).

22
form of economic obsolescence, as opposed to physical depreciation.13

To finance the new capital, the firm must obtain funding from a bank.14

For each new unit of capital it acquires it issues a state-contingent claim to

the future stream of earnings from the unit: +1+1(1−)+1+2+2(1−

)2+1+2+3+3 etc. As we discussed earlier, banks are able to perfectly

monitor firms and enforce contracts. As a result, through competition, the

security the firm issues is perfectly state-contingent with producers earning

zero profits state-by-state. In addition, the value of the security  is equal

to the market price of the capital underlying security. Finally, the period

 + 1 payoff is (+1 + (1 − )+1)+1: the sum of gross profits and the

value of the leftover capital multiplied by the capital quality shock, which

corresponds to the definition of the rate of return in equation.(5).

Before proceeding, it is worth emphasizing that the financial frictions

that banks face in obtaining funds from depositors affect the cost of capital

to non-financial firms. As we saw in the section 2.2, the capital constraints

on banks limit the supply of funds they can intermediate, which raises loan

rates. As we illustrate later, a financial crisis sharply tightens these capital

constraints.

3.1.2 Capital Goods Producers

Capital producers make new capital using input of final output and subject

to adjustment costs. They sell the new capital to firms at the price  Given

that households own capital producers, the objective of a capital producer is

13ne way to motivate this disturbance is to assume that final output is a C.E.S. composite

of a continuum of intermediate goods that are in turn produced by employing capital and

labor in a Cobb-Douglas production technology. Suppose that, once capital is installed,

capital is good-specific and that each period a random fraction of goods become obsolete

and are replaced by new goods. The capital used to produced the obsolete goods is now

worthless and the capital for the new goods is not fully on line. The aggregate capital

stock will then evolve according to equation (32).

14For simplicity only, we assume that all non-financial firms are homogenous in their

access to credit. As emphasized by Gertler and Gilchrist (1994), and Bernanke, Gertler

and Gilchrist (1996), firms have heterogenous access to credit, ranging from those who

must exclusively rely on bank credit to those that can meet their financing needs mainly

from open market credit. Both Bernanke and Gertler (1989) and Bernanke, Gertler and

Gilchrist (1999) present models which allow for firm heterogeneity in credit access. The

latter shows that so long as there are output complementarities across firms with differential access to credit, a "heterogenous" firm model can produce cyclical dynamics similar

to a "homogenous" firm model.

23
to choose  to solve:

max 

X∞

=

Λ 1⁄2



  −

∙

1 + 

μ 

−1

¶ ̧ 3⁄4

(33)

From profit maximization, the price of capital goods is equal to the marginal

cost of investment goods production as follows,

 =1+ 

μ 

−1

¶

+



−1

0( 

−1

) − Λ+1(

+1



)

2

0(

+1



) (34)

Profits (which arise only outside of steady state), are redistributed lump sum

to households.

3.1.3 Retail Firms

Final output  is a CES composite of a continuum of mass unity of differentiated retail firms, that use intermediate output as the sole input. The final

output composite is given by

 =

∙Z 1

0

 

−1

  ̧ 

−1

(35)

where   is output by retailer .

Retailers simply re-package intermediate output. It takes one unit of

intermediate output to make a unit of retail output. The marginal cost

is thus the relative intermediate output price  We introduce nominal

rigidities following Calvo. In particular, each period a firm is able to freely

adjust its price with probability 1 − . Accordingly, each firms chooses

the reset price ∗

 to maximize expected discounted profits subject to the

restriction on the adjustment frequency. Following standard arguments, the

first order necessary condition for this problem is given by:

X∞

=0

Λ+

∙ ∗



+

− +

 ̧

 + = 0 (36)

with  = 1

1−1  From the law of large numbers, the following relation for the

evolution of the price level emerges:

 = £

(1 − )(∗

 )

1− + (−1)1−

¤ 1

1− (37)

24
3.2 Government Policy

Government expenditures are composed of: government consumption, which

we hold fixed at  and the net interest payments from an exogenously fixed

stock of long term government debt, which we set at  Revenues consist of

of lump sum taxes and the earnings from central bank intermediation net

transaction costs. As discussed in section 2.3, central bank asset purchases

are financed by short term government debt. Given the central bank balance

sheet (19), we can express the consolidated government budget constraint as:

+(−1) = +(−− )−1−1+(−− )−1−1 (38)

We suppose monetary policy is characterized by a simple Taylor rule. Let

 be the net nominal interest rate,  the steady state nominal rate, and  ∗



the natural (flexible price equilibrium) level of output. Then:

 =  +  + (log  ∗

 − log ) +  (39)

and where  is an exogenous shock to monetary policy, and where the link

between nominal and real interest rates is given by the following Fisher relation

1 +  = +1

+1



(40)

We suppose that the interest rate rule is sufficient to characterize monetary policy in normal times. In a crisis, however, we allow for large scale asset

purchases. In particular, we suppose that at the onset of a crisis, which for we

define loosely to mean a period where excess returns rise sharply, the central

bank purchases the fraction  of the outstanding stock of private securities

and the fraction  of the outstanding stock of long term government bonds:

 =  (41)

 = 

where both  and  obey second order stationary stochastic processes. In

the next section we clarify how the central bank intervenes in a crisis with

asset purchases.

3.3 Resource Constraint and Equilibrium

Output is divided between consumption, investment, government consumption, and expenditures on central bank intermediation Φ. The economy-wide

resource constraint is thus given by

25
 =  + [1 + 

μ 

−1

¶

] +  + Φ (42)

with Φ =  −1−1 +  −1−1

Finally, to close the model, we require market clearing in markets for

private securities, long term government bonds and labor. The supply of

private securities at the end of period  is given by the sum of newly acquired

capital  and leftover capital (1 − )  :

 =  + (1 − )  (43)

The supply of long term government bonds is fixed by the government

 =  (44)

Finally, the condition that labor demand equals labor supply requires

that

(1 − )





·  = 1





 (45)

where the inverse of the price of intermediate goods 1

 is effectively the

retail goods price markup. As we show, this markup can rise in a crisis,

enhancing the contraction in employment.

We note that because of Walras’ Law, once the market for goods, labor,

and long term securities, cleared, the market for riskless short term debt will

be cleared automatically. As we discussed, the short term government debt

may either be directly held by households or instead by banks who in turn

issue deposits to households. In the latter case, one can interpret the debt

as interest bearing reserves. This completes the description of the model.

4 Model Analysis

Our goal here is to provide concrete numerical examples to illustrate the

qualitative insights about the effects of LSAPs developed in section 2.

4.1 Calibration

Table 1 lists the choice of parameter values for our baseline model. Overall

there are twenty parameters. Twelve are conventional. Eight (  ∆  



26


  ) are specific to our model.15

We begin with the conventional parameters. For the depreciation rate 

the capital share , the elasticity of substitution between goods, , and the

government expenditure share, we choose standard values. For the discount

factor  we assign a quarterly value of 0995 which implies a steady state

short term interest rate of two percent. Following the literature on the zero

lower bound, we choose a low steady state real rate to increase the likelihood

that the ZLB is binding in the crisis experiment that we study. For the other

conventional parameters we use estimates from Primiceri, Schaumburg and

Tambalotti (2006) to obtain values. These parameters include: the habit

parameter ; the inverse elasticity of investment to the price of capital ;

the relative utility weight on labor ; the Frisch elasticity of labor supply

−1; and the price rigidity parameter,  Since the policy rule the authors

estimate is somewhat non-standard, we use instead the conventional Taylor

rule parameters of 15 for the feedback coefficient on inflation, , and 05 for

the output gap coefficient,  For simplicity, we use minus the price markup

as a proxy for the output gap.

Our choice of the financial sector parameters is meant to be suggestive.

We choose a survival probability  = 0975 that implies an expected horizon

of ten years for bankers. We set  so that in steady state households

hold half the quantity of private securities and  so that households hold

three quarters of the outstanding stock of long term government debt. We

choose values for , ∆ and  to hit the following targets; a steady state

excess return on government bonds of fifty basis points a steady state excess

return on private securities of one hundred basis points, and a steady state

leverage ratio for banks of six. We base the steady state target for the excess

return on bonds on estimates of the term premium by Ludvigson and Ng

(2009) using pre-crisis data. For private securities we use information on

the pre-2007 spreads between mortgage rates and government bonds and

between BAA corporate vs. government bonds, in conjunction with the

evidence on the term premium. The steady state leverage ratio is trickier

to calibrate. For investment banks and commercial banks, which were at

the center of the crisis, leverage ratios (assets to equity) were extraordinarily

15We simply fix the parameters which reflect the efficiency costs of central bank intermediation,   and   equal to zero since under reasonable values they do not affect model

dynamics. They will matter for welfare calculations, but we do not do these here. See

Gertler and Karadi (2011) for an analysis.

27
high: typically in the range of fifteen to twenty for the former and eight

to ten for the latter. However, everything else equal, our model overstates

the risk from asset price fluctuations that banks face since they essentially

hold equity claims: In practice creditors share more of the risk with banks.

Accordingly, we compensate by assuming a steady state leverage ratio that

is roughly half the average across banking institutions. The reduced leverage

ratio dampens the impact of asset price fluctuations on bank net worth.

We choose the household portfolio adjustment cost parameter  so that the

model approximates the evidence on the impact of effect of QE2 on both real

activity and the ten year bond rate. It will turn out that  = 1 reasonably

satisfies this requirement. Finally,  is set to have the ratio of the stock

of long term government bonds to (steady state) output equal its pre-crisis

value of approximately 045.

Finally, to be consistent with the much of the evidence of LSAPs, within

our simulations we report the behavior of yields to maturity of ten year bond

rates on securities that have equivalent value to the respective infinite horizon

claims in the model. In the case of the long term government bond, we

consider a ten year equivalent government debt that has an identical price to

the consol in the baseline model, but a slightly different payoff structure: For

the first forty quarters it yields a a coupon payment identical to the consol

(i.e., unity per period). The quarter after there is a "principal" payment

equal to the nominal steady state price of the consol 

 = 1( −1) where

 is the steady state nominal interest rate. The nominal yield to maturity

on the ten year government bond 

∗

 is accordingly

 = X

40

=1

1

(1 + 

∗

) + 



(1 + 

∗

)40 (46)

where  the nominal price of the bond (equal to the price of the equivalent

consol) and 

 is the terminal payment of the bond. The yield to maturity

on the analogous ten year private security is given by

 = 

X

40

=1

(+ − +)+

(1 + 

∗

) +

+40

(1 + 

∗

)40 (47)

28
4.2 Model Simulations

We begin with several simulations designed to illustrate how LSAPs affect

real activity and inflation in our model economy. We start with a basic exercise that compares how similar size purchases of private versus government

securities affect the economy. We then compare the government bond purchase program under QE2 to a conventional interest rate policy. That is, we

find the interest rate policy that provides roughly equivalent stimulus to the

bond purchase program. Next, we analyze how the strength of the impact

of LSAPs is affected by whether the zero lower bound is binding. We then

explore the implications of household participation in long term securities

markets. Finally, we consider a financial crisis within the model that has

some of the key features of the one that the global economy had in the late

2008 early 2009. We then explore the effects of asset purchase programs

similar in nature to what occurred under QE1.

In Figure 1, the panels report the responses of the model economy to an a

LSAP similar in size to QE2. The solid line reports the response to purchases

of long term government bonds, as actually occurred under QE2. The dotted

lines report the effects of a similar size purchase of private securities. The

purchases were phased in over a roughly six month period and the cumulative

total equaled approximately two and a half percent of GDP. By this, we are

approximating the size of purchases in terms of ’10-year-equivalents’ that

incorporates their maturity structure.16 Following Chen, Curdia and Ferrero

(2011), we suppose that the purchases are kept at the peak for two years

and are gradually phased out, though we approximate this pattern with a

second order order autoregressive process. We also follow these authors by

appealing to evidence from the Fed Funds futures market which suggested

that the Funds rate was likely to remain fixed for a year after the purchases

were initiated. Accordingly, in the experiment we keep the Funds rate fixed

for the first four quarters and then let it revert to the Taylor rule described

earlier. Finally, we fixed the portfolio adjustment cost parameter  to ensure

that the QE2 experiment produce a reduction in the ten year government

bond rate 10 of twelve basis points, which is within the range of estimates in

Williams (2011) and elsewhere. We then explore how the rest of the model

economy responds to our QE2 simulation before going on to consider a variety

16 $600bn translate into $374bn in ten-year equivalents based on the

planned maturity breakdown of the Federal Reserve Bank of New York.

http://www.newyorkfed.org/markets/lttreas_faq.html

29
of other experiments.

As the figure shows, the decline in long term rates produces a peak increase in output of one percent, which is closely in line with the time series

estimates of Gambacorta, Hoffman, and Peersman (2011). There is also an

increase in inflation and asset prices, which is consistent with the event study

evidence for QE2.17 Overall, the response of the standard macroeconomic

variable mirrors the response to a conventional monetary policy easing. We

stress, though, that LSAPs work ultimately by reducing excess returns. Underlying the drop in the long term bond rate is a decline in the current and

expected sequence of one period excess returns [] − , as panel 9. in

Figure 1. shows. We can isolate the component of the drop in the ten year

government bond rate that is due to a decline in excess returns by examining

the spread between 10 and the yield to maturity on the ten year ’risk-free’

swap rate 10 (i.e. the rate on a security that pays the short rate each quarter for ten years that would be priced by the household if it were allowed to

hold it). As the figure indicates, the lion’s share of the drop in the ten year

government bond rate - roughly ten of the overall twelve basis point drop -

is due to a decline in excess returns.

The LSAP also reduces the yield to maturity on the private security

10 by nearly double the drop in the rate on government bonds (which can

be seen by noting that the spread 10 − 10 declines ten basis points on impact.)18 The decline in 10 is key for the transmission of the LSAP to the real

economy. It causes the asset price  to increase, which in turns stimulates

investment spending. As discussed in section 2.3, 10 moves proportionately

more than 10 in response to the LSAP because for banks — the marginal

traders in the securities markets — agency costs of financing privates secu17The counterfactual jump in inflation in the initial period occurs because we have

abstracted from the usual frictions that tend to smooth inflation such as wage rigidity

and so on. However, averaging over the first five years, the increase in inflation is roughly

seventeen basis points, which is in line with the event study evidence for QE2 (see, for

example, Krishnamurthy and Vissing-Jorgensen, 2011.)

18The relative effect of government bond purchases on private security yields is an

open question. Krishnamurthy and Vissing-Jorgensen (2011) present careful event study

evidence from the QE2 period suggesting that default corrected corporate yields moved

one-for one with government bond yields, using CDS spreads to correct for default risk.

The issue here is how reliable CDS spreads are as pure measures of default risk if CDS

providers themselves are financially constrained. It is also true that AMBS rates moved

by less than government bond yields during this episode. At this time, however, the Fed

was effectively the dominant holder of AMBS.

30
rities are proportionately greater than for government bonds (see equation

(22)).

Finally, Figure 1 shows that an equivalent size purchase of the private

security has roughly double the effect on long term bond yields and the rest

of the economy. This kind of differential effect is consistent with the rough

evidence19. As we emphasized in section 2.3, a central bank purchase of the

private security relaxes banks’ balance sheet constraint proportionately more

than a similar size purchase of government bonds, which enhances the market

demand for securities. The exact difference depends on the assumption about

the strength of the agency friction that inhibits arbitrage in each case. But

so long as the friction is greater for private securities than for government

bonds, purchases of the former will have stronger effects than of the latter.

Figure 2 identifies the conventional interest policy that provides stimulus

equivalent to the government bond LSAP portrayed in Figure 1. In particular

we suppose that the central bank reduces the short term interest rate in the

first period and then keeps it fixed at this level for a total of four quarters, the

length of time it was fixed in the QE2 experiment. Then as in the latter case,

we allow the interest rate to revert to the Taylor rule. As the figure shows,

the conventional monetary policy that corresponds to our approximation of

QE2 is a forty basis point reduction in the short rate for a period of a year.20

Interestingly, this result comes close to the rule of thumb many in the Fed

use that a reduction in long rates from monetary stimulus corresponds to

a threefold reduction in short rates. It is also interesting to observe from

comparing the inflation responses that the inflation generated by the LSAP

is nearly identical to that created by the "equivalent" monetary policy. This

occurs of course because inflation under the LSAP is ultimately the product

19For example, Gagnon et. al (2011) show the announcement effect of the initial wave

of QE1 in December 2008 led to a reduction in long term government bond rates of 67bps

versus estimates of roughly 15 bps for QE2 (see Williams, 2011). After we adjust for

the fact that this first phase of QE1 involved about one and a half times the amount

of purchases done under QE2, we still get a larger drop in long rates from QE1, which

involved mostly AMBS purchases, than from the government bond purchases under QE2:

approximately 44 bps. versus 15 bps. Of course there is a huge amount of noise underlying

these estimates. Other studies similarly find stronger effects of QE1 (adjusting for size).

20Though we do not report the results here, our estimate of the interest policy that

approximates QE1 would be a reduction in the short rate of 240 basis points for a period

of a year. This estimate comes from the fact that QE1 was roughly three times the size of

QE2 and, within our model, a dollar purchase of the private security has twice the effect

on long rates as a similar purchase of government bonds.

31
of the stimulus provided from interest rate reduction, as is the case with

interest rate policy. There is no independent effect of the size of the balance

sheet on inflation. Of course, were the central bank to take significant losses

on its balance sheet that could only be financed by exorbitant money creation,

matters would change. But at least currently, this does not appear to be a

danger facing the Fed’s balance sheet.

Figure 3 addresses the issue of how the zero lower bound affects the

impact of the LSAP. We compare our baseline scenario where short rates are

expected to be fixed for a year to one where they adjust immediately. As

the figure shows, the immediate adjustment of short rates offsets more than

eighty percent of the effect of the LSAP on output. The rise in short rates

generated by the Taylor rule is rough thirty basis point for the first year,

which as implied by Figure 2 mostly offsets the stimulus from the LSAP.

Thus it makes sense to use LSAPs only in situations where short rates are

expected to remain fixed for a considerable period of time.

In Figure 4 we illustrate the implications of imperfectly elastic household

demands for long term securities. We consider an alternative to our baseline

where households only hold short term securities and banks hold the entire

stock of long term private securities and government bonds. The impact of

LSAPs is clearly weaker in this alternative scenario: The long term bond

rate drops only about five basis points as opposed to twelve in the baseline

and the increase in output is only about half the baseline case. Intuitively,

in the baseline, imperfectly elastic household demands works to "segment"

asset markets. In effect, the pool of actively traded securities is reduced: A

given change in central purchases then has a greater proportionate effect in

the market for actively traded securities, causing asset prices and returns to

respond accordingly. This impact of friction in household asset demands on

the strength of LSAPs accords well with conventional wisdom. We stress,

however, that it is also critical, that the marginal traders, i.e., the banks,

also face limits to arbitrage. As we showed in section 2, absent these limits,

LSAPs are neutral even with imperfectly elastic household demand.

We now explore how LSAPs work in the context of a financial crisis that

has some key features of the one that recently occurred in the wake of the

Lehman Brothers collapse. In particular, we use the model to illustrate

how an LSAP program with features similar to QE1 may have worked to

moderate the downturn. One distinguishing feature of the policy experiments

we perform is that the number of periods the zero lower bound binds is

endogenous, in contrast to the earlier experiments where the short was held

32
fixed for a given number of periods.

We stress that we are not attempting a complete description of the crisis:

The model is too simple for this. We are however able to create a recession

where financial intermediation is disrupted in a way that raises the cost

of credit, which in turn amplifies the downturn. Further, the downturn is

sufficiently sharp to push the economy to the point where the zero lower

bound on the nominal interest rate is binding. In this way we capture the

two features of the crisis that are most relevant in are view for the role of

LSAPs.

The initiating shock for the crisis is a decline in capital quality.21 The

reduction in the value of bank assets forces a fire sale of bank assets to

satisfy the balance sheet constraint. Asset prices decline and excess returns

rise, which depresses real activity. The process is amplified as the asset

fire sale and decline in real activity further weaken bank balance sheets.

We suppose the the shock obeys a first order autoregressive process with

coefficient 07 (so that it mostly dies out after a year and half). Then to

produce a sharp output contraction in the first two quarters (as occurred

after the Lehman collapse), we hit the model economy with two consecutive

unanticipated negative capital quality shocks: The first is a 3.3% decline and

the second is just large enough to offset the mean reversion in the variable

for one period.

We also suppose that an LSAP program involving the purchase of the

private security is initiated in the wake of the shock. The sequencing of

the purchases as well as the overall size at the peak is meant to be similar

to QE1. In December 2008 the initial purchase program was announced

that was equal to roughly half the eventual size. The announcement of

the second stage of the program came in March 2009. In the meantime a

number of temporary complementary measures, including the commercial

paper funding facility were set up in 2008 Q4. Accordingly, we assume that

the policy is phased in as a sequence of three unexpected shocks with the first

shock accounting for one quarter of the total cumulative effect and the next

two the remaining three quarters, divided evenly among each. To capture the

cumulative buildup, the shocks obey second order autoregressive processes

the with the first lag coefficient equal to 15 and the second equal to −055

21 In Gertler and Karadi (2011), we show that simply beliefs that asset values will fall

in the future can generate a crisis similar to that generated by a decline in capital quality.

How to tie down beliefs, however, is an issue.

33
The peak of the LSAP is six percent of GDP, consistent with the evidence

on ten-year equivalent purchases.

Figure 5 illustrates the crisis experiment under three different scenarios:

(1) no central bank response; (2) an LSAP similar to QE1; (3) an LSAP

similar in timing and magnitude to QE1, except that the central bank purchases government bonds instead of the private security. Figure 6 reports

how much difference the LSAPs made to the response of the model economy

under both scenarios (2) and (3).

Under each case there is a sharp drop in output and an associated increase

in credit spreads. The latter serves to propagate the downturn. The "QE1"

LSAP moderates the decline substantially. The output drop is roughly three

and a half percent lower relative to the case without central bank intervention. The policy works by reducing both interest rate and interest rate

spreads by amounts in accord with the evidence. It reduces the long term

bond rate roughly thirty basis points for a period of more than two years

and reduces the yield on the long term private security by roughly fifty five

basis points, also for a sustained period. Underlying this reduction in rates,

is a reduction in one period excess returns on both the private security and

government bonds.

Substituting long term government bond purchases for private sector purchases weakens the effect of the LSAP by a factor of roughly one third. This

differential is smaller than in the "non-crisis" experiments we did earlier. The

reason is that the horizon over which the short term interest rate is constant

is endogenous in this case, whereas it was fixed earlier. The purchases of

private securities shortens the period of time the economy remains at the

zero lower bound by a quarter, weakening the overall impact. The overall

effect, however, remains stronger than if government bonds were purchased

instead.

We stress that the crisis experiment focuses on the immediate period

around the Lehman collapse and the QE1 intervention. The model is not

set up to capture the duration of the crisis. Factors such an overhang of

the housing stock, household indebtedness, and global spillovers of economic

distress that have contributed to delaying the recovery are not considered.

Thus, one should interpret these exercises as an attempt to tease out the

nature and strength of the transmission mechanisms for LSAPs, and not an

attempt to provide a complete historical account of the recession.

Finally, as a check on the model, we note that a recent paper by Adrian,

Colla and Shin (2012) documents four facts any macroeconomic model of

34
financial crises should have to explain: (1) a disruption in the flow of bank

credit; (2) a sharp increase in credit spreads; (3) a rise in open market credit

relative to bank credit (i.e., bond financing relative bank loans; and (4)

procyclical bank leverage ratios. The authors then conclude that most macro

models of financial crises can capture (1) and (2) but not (3) and (4).

Here we demonstrate that our model can account for all four facts. Figure

7 repeats the same experiment as in figure 6, this time portraying the response

of the bank versus open market credit flows and the bank leverage ratio.

The decline in asset quality produces a sharp contraction in the net worth of

banks (see the second panel in the bottom row). The leads to a contraction

in bank loans (see the second panel in the middle row) and a rise in the

spread between the loan rate and government bond rate (see the third panel

in the top row.) Thus, the model captures facts 1 and 2. It also captures

fact 3: New bond issues increase as the tightening of bank lending induces

firms to substitute to open market credit (see the first panel in the middle

row.)

Finally, the model is able to match the cyclical behavior of bank leverage

ratios, assuming the leverage ratios from the model simulations are constructed the same way they are in the data. In particular, in the data, bank

equity is computed as the difference between assets and liabilities, where assets are measured using "fair value" accounting which in practice is a mixture

of book value and market value accounting. Fair value accounting, further,

uses market prices when available, but during a liquidity disruption where

trade may be disrupted, instead uses a "normal" value, which is effectively a

smoothed value. Thus, bank equity as measured in the data is less procyclical than true market values would suggest22. Since leverage is procyclical

and measured equity is relatively acyclical, measured bank leverage ratios

are thus procyclical. By contrast, equity in the model is in terms of market

value, which is highly procyclical, leading to a countercyclical leverage ratio

22The fair value adjustment we use assumes that the ’fair value’ assets of the banks

are a weighted average of market value and book value. The weight on market value is

0.25 and on book value 0.75. In reality, 50% of assets follow fair value accounting (while

the other 50% is on book value according, see SEC (2008)) and we have further halved

this number to reflect the fact that even fair value does not mean mark-to-market during

fire-sales (as fair value is a price on which the bank would be willing to sell). The book

value of capital, furthermore, is assumed to disregard the effect of capital quality shock,

and is only influenced by the observed drop in the investment. Book and market value of

deposits are the same, and book value of net worth is calculated as a difference between

book value of assets and deposits.

35
(see the first panel in the third row). However, when bank equity in the

model is measured the same way as it is in the data, then the model leverage

ratio becomes procyclical, as the first two panels of the bottom row indicate.

5 Concluding Remarks

A popular view of LSAPs — known more broadly as "quantitative easing" —

is that they reflect money creation. We instead argue that LSAPs should be

seen as central bank intermediation. Just like private intermediaries the Fed

has financed its asset purchases with variable interest bearing liabilities and

not money per se. The difference of course is that that Fed’s liabilities are

effectively government debt. Thus the Fed’s is able to obtain funds elastically

in a way that private intermediaries facing financial market frictions are

not. As we have shown, it is because of these limits to arbitrage in private

intermediation that LSAPs can be effective. It is also worth emphasizing

that effectiveness of LSAPs within our model is not due to the central bank

being more efficient at holding assets than the private sector: In fact, we

assume the opposite.

While the details of transmission differ, as with conventional monetary

policy, LSAPs stimulate the economy by reducing credit costs. Thus, as we

have shown, the transmission to real output and inflation is very similar to

that occurring under conventional policy. Unlike conventional policy, however, LSAPs are an option when when the zero lower bound is binding. In

addition, as we have shown, LSAPs are actually most effective in this situation: Holding constant the size of the purchase and the type of the security,

an LSAP leads to a larger reduction in long rates the longer is the horizon

over which short term rates are expected not to rise.

The framework we presented was designed to provide a unified way to

think about the various LSAP programs that the Fed has pursued over the

course of the recent crisis. We think that it may also be useful for analyzing

new programs under consideration, as well as some LSAPs pursued by other

central banks.

For example, under consideration at the Fed is "sterilized" QE, which

basically involves lengthening the maturity of the liabilities issued to fund

asset purchases from overnight to up to six months. In addition, investors

other than banks can hold these liabilities. With sterilized QE, our interpretation of LSAPs as central bank intermediation if anything becomes more

36
obvious. Again, key to the effectiveness of these types of LSAPs are limits

on private intermediaries’ ability to fund the same long term securities by

issuing liabilities of same (short term) maturity as the central bank.

Finally, though the details differ, the recent long-term refinancing operations (LTROs) undertaken by the ECB have a similar flavor to the LSAPs

we have been analyzing. Under the LTROs, the ECB does not directly purchase assets: But it does so indirectly by accepting the assets as collateral

for loans to participating banks. In particular, it provides three year variable

rate credit to banks for loans collateralized by assets it deems acceptable,

including certain government bonds, certain asset-backed securities and even

certain types of bank loans. The haircuts on the collateral vary according to

the risk class. As with LSAPs, for LTROs to be effective, private intermediaries must be limited in their ability to perform the same type of arbitrage

as the central bank. We leave for future research, however, working out the

modifications of the model needed to precisely capture LTROs.

37
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41
Table 1: Asset holdings of leveraged and non-leveraged institutions

Domestic net assets (Billions,$) %

all leveraged non-lev’d leveraged non-lev’d

Total Mortgages 14336 6170 8166 43.0% 57.0%

Agency MBS 3590 1567 2023 43.6% 56.4%

Treasuries & 4195 1325 2870 31.6% 68.4% Agency debt

Treasuries 1876 312 1563 16.7% 83.3%

Source: Flow of Funds, 2008 december

Leveraged institutions: Commercial Banks, Savings Banks, Credit Unions, Brokers and Dealers, Government Sponsored Enterprises, Finance Companies

Agency debt and Agency MBS is not published separately for different financial intermediaries. We

assume each are held proportionally to their combined holdings by leveraged and non-leveraged institutions.
Table 2: Parameters

Households

β 0.995 Discount rate

h 0.815 Habit parameter

χ 3.482 Relative utility weight of labor

B/Y 0.450 Steady state Treasury supply

K ̄ h/K 0.500 Proportion of direct capital holdings of the HHs

B ̄h/B 0.750 Proportion of long term Treasury holdings of the HHs

κ 1.000 Portfolio adjustment cost

φ 0.276 Inverse Frisch elasticity of labor supply

Financial Intermediaries

θ 0.345 Fraction of capital that can be diverted

∆ 0.500 Proportional advantage in seizure rate of government debt

ω 0.0007 Proportional transfer to the entering bankers

σ 0.972 Survival rate of the bankers

Intermediate good firms

α 0.330 Capital share

δ 0.025 Depreciation rate

Capital Producing Firms

ηi 1.728 Inverse elasticity of net investment to the price of capital

Retail Firms

 4.167 Elasticity of substitution

γ 0.779 Probability of keeping the price constant

Government

G

Y

0.200 Steady state proportion of government expenditures

κπ 1.500 Inflation coefficient in the Taylor rule

κX -0.125 Markup coefficient in the Taylor rule
0 20 40

0

1

2

3

CB purchases

% of GDP

0 20 40

−1

0

1

2

3

Y

%

∆ from ss

Private asset purchase Government bond purchase

0 20 40

−1

0

1

2

3

π

0 20 40

−1

0

1

2

i

0 20 40

−4

−2

0

2

R

%

∆ from ss

0 20 40

−2

0

2

4

6

Q

0 20 40

−10

0

10

20

30

N

0 20 40

−3

−2

−1

0

1

E[Rk]−R

0 20 40

−1.5

−1

−0.5

0

0.5

E[Rb]−R

%

∆ from ss

Quarters

0 20 40

−0.4

−0.3

−0.2

−0.1

0

i

b10

Quarters

0 20 40

−0.2

−0.1

0

0.1

0.2

i

b10−ii10

Quarters

0 20 40

−0.2

−0.1

0

0.1

0.2

i

k10−ib10

Quarters

Figure 1: Private and government asset purchase shocks. Purchases are calibrated to a

peak effect of 2.5% of GDP and interest rates are kept unchanged for 4 periods.
0 20 40

0

0.5

1

1.5

2

2.5

3

Shocks

% of GDP

0 20 40

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

Y

%

∆ from ss

Government bond purchase Monetary policy shock

0 20 40

−0.5

0

0.5

1

1.5

2

π

0 20 40

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

i

%

∆ from ss

Quarters

0 20 40

−0.2

−0.15

−0.1

−0.05

0

i

b10

Quarters

0 20 40

−0.12

−0.1

−0.08

−0.06

−0.04

−0.02

0

0.02

i

k10−ib10

Quarters

Figure 2: Monetary and government bond purchase shocks. The government bond

purchase shock is calibrated to a peak effect of 2.5% of GDP with interest rates kept

unchanged for 4 periods. The monetary policy shock reduces the nominal interest rate

by 40 basis-points below its steady state value for 4 periods.
0 20 40

0

0.5

1

1.5

2

2.5

3

CB purchases

% of GDP

0 20 40

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

Y

%

∆ from ss

No interest rate response Interest rate response

0 20 40

−0.5

0

0.5

1

1.5

π

0 20 40

−0.5

0

0.5

1

i

%

∆ from ss

Quarters

0 20 40

−0.15

−0.1

−0.05

0

0.05

i

b10

Quarters

0 20 40

−0.1

−0.08

−0.06

−0.04

−0.02

0

0.02

i

k10−ib10

Quarters

Figure 3: Government bond purchase shocks with and without interest rate responses.

The bond policy is calibrated to a peak effect of 2.5% of GDP. The interest rate is kept

unchanged for 4 periods.
0 20 40

0

0.5

1

1.5

2

2.5

3

CB purchases

% of GDP

0 20 40

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

Y

%

∆ from ss

Not segmented HH asset markets Segmented HH asset markets

0 20 40

−0.5

0

0.5

1

1.5

π

0 20 40

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

i

%

∆ from ss

Quarters

0 20 40

−0.12

−0.1

−0.08

−0.06

−0.04

−0.02

0

i

b10

Quarters

0 20 40

−0.1

−0.08

−0.06

−0.04

−0.02

0

0.02

i

k10−ib10

Quarters

Figure 4: Government bond purchase shocks with and without segmented household

asset markets. Purchases are calibrated to a peak effect of 2.5% of GDP and interest

rates are kept unchanged for 4 periods.
0 20 40

−4

−3

−2

−1

0

%

∆ from ss

e

ξ

No policy Private asset purchase Government bond purchase

0 20 40

−10

−5

0

Y

0 20 40

−10

−5

0

5

π

0 20 40

−4

−2

0

2

4

i

0 20 40

−4

−2

0

2

4

R

%

∆ from ss

0 20 40

−20

−10

0

10

Q

0 20 40

−150

−100

−50

0

N

0 20 40

−10

0

10

20

E[Rk]−R

0 20 40

−5

0

5

10

E[Rb]−R

%

∆ from ss

Quarters

0 20 40

0

0.5

1

i

b10−ii10

Quarters

0 20 40

0

1

2

3

i

k10−ib10

Quarters

0 20 40

0

2

4

6

8

Purchases

% of GDP

Quarters

Figure 5: Crisis experiment. Reactions to two consecutive unexpected capital quality

shocks with gradual private and government asset purchases with the zero-lower bound.
0 20 40

0

1

2

3

4

5

6

7

Purchases

% of GDP

Private asset purchase Government bond purchase

0 20 40

−1

0

1

2

3

4

Y

%

∆ from ss

0 20 40

−1

0

1

2

3

4

5

π

0 20 40

−2

−1

0

1

2

3

4

i

%

∆ from ss

Quarters

0 20 40

−0.4

−0.3

−0.2

−0.1

0

i

b10

Quarters

0 20 40

−0.4

−0.3

−0.2

−0.1

0

0.1

i

k10−ib10

Quarters

%

∆ from ss

Figure 6: Effects of private and government asset purchases following the crisis experiment. The figures plot the differences from a no-policy-response case.
0 10 20 30 40

−4

−3

−2

−1

0

%

∆ from ss

e

ξ

0 10 20 30 40

−6

−4

−2

0

Y

%

∆ from ss

0 10 20 30 40

0

0.5

1

1.5

2

i

k10−ib10

%

∆ from ss

0 10 20 30 40

0

2

4

6

8

Kh

%

∆ from ss

0 10 20 30 40

−40

−30

−20

−10

0

Kb

%

∆ from ss

0 10 20 30 40

−30

−20

−10

0

D

%

∆ from ss

0 10 20 30 40

−50

0

50

100

φ

Quarters

%

∆ from ss

0 10 20 30 40

−150

−100

−50

0

50

N

Quarters

%

∆ from ss

0 10 20 30 40

−15

−10

−5

0

5

K

Quarters

%

∆ from ss

Baseline Adjusted "Fair" Value

Figure 7: Crisis experiment with adjusted ’fair’ book values and market values.