‘

Clarendon Lectures

Lecture 1_________EVIL IS THE ROOT OF ALL MONEY

by

Nobuhiro Kiyotaki
London School of Economics

andJohn Moore
Edinburgh University and London School of Economics

26 November 2001

1

It is an honour to have been invited to give the Clarendon lectures.
Thank you.
L.S.E.

My lectures are based on joint research with Nobu Kiyotaki of theI was originally scheduled to perform here a year ago, but we werestill in the midst of our research then.
is like sausages.

You know the old saying: research

The finished article can be delicious.

want to see what goes into the making of it.

But people don’t

Had I told you about our

research last November, it would have been just offal.

So I asked Andrew

Schuller of O.U.P. to postpone the lectures, and he kindly agreed.

The extra

time has allowed us to develop the research, especially for tomorrow’s
lecture.

The sausages are now seasoned, and ready for the table.

The overall title for the lecture series is "Money and Liquidity".

But

let me say straight away that, of these two, we think liquidity is the key.
Money -- that is, non-interest-bearing fiat money -- is merely theconsequence of a liquidity shortage.
a logical necessity.

As I shall explain later, money is not

Indeed, money may eventually disappear.

It may be

driven out by ultra-liquid, privately-issued securities that earn interest.
In our view, Monetary Economics should be displaced by Liquidity Economics.

That said, it is useful to start with money.

From the title of thisevening’s lecture, "Evil is the Root of all Money", some of you may have come
expecting me to talk about morality as well as money.

Well, you won’t bedisappointed.

I will.

The ratio of morality to money will be low, but thetitle is apt.

It expresses what we think should be at the heart of a theoryof money.

I should put my cards on the table.

I am a microeconomist.

So pleaseforgive my temerity in coming before you to lecture about these macroeconomic
topics: money and liquidity.

Tomorrow evening’s lecture will touch on

government, and monetary policy.

Wednesday’s lecture concerns systemic risk,

and the role a government might play in supplying liquidity to avert afinancial crisis.

My only defence for venturing into these areas is that my collaborator,
Nobu Kiyotaki, is a distinguished macroeconomist.
work with Nobu.

It is very good fun too.

It is a great privilege to

Research with him is an example ofthose curious technologies for which input and consumption are one and the2same thing.

Together, he and I are engaged in a pincer movement:

he brings

his money-macro expertise, and I bring my experience of working with Oliver
Hart on matters to do with power and control in financial contracting.

Money.

Money is strange stuff.

Take these Scottish pound notes.

They’re useless: they have no intrinsic value.
willing to hold them?
money.

So why should anyone beThat is the classic question economists ask about

The answer seems obvious: people find it difficult to barter.

I

don’t offer my dentist an economics lesson in exchange for fixing my teeth.
It’s hard for people to find a "double coincidence of wants".
use money to buy goods.

Instead, they

The dentist accepts money, not because she wants

money as such, but because she anticipates that she can use it later to buy
what she does want.

Money is the medium of exchange.

Notice that for this argument to hold together, there has to be set ofmutually-sustaining beliefs, stretching off to infinity.

I was willing tohold money yesterday because I believed the dentist would accept it today.
She is willing to hold money today because she believes someone else will
accept it tomorrow.

And so on.

If there were a known end-point to history,

the entire structure of beliefs would collapse back from the end.

Nevertheless, with infinity on our side, we have arrived at the classic
answer to our classic question: people are willing to hold money because it
helps them do business with each other.

It is the oil that lubricates the

economic machine.

Unfortunately, this classic answer to our question about money iscompletely at odds with the classic answer we give to nearly all otherquestions in economics!

One of the most useful tools of our trade is thenotion of perfect competition.

In a perfectly competitive framework, there

are no frictions to impede trade, so we don’t need money as a lubricant.

The

story goes like this: the dentist, the economist, and everyone else, gettogether in a marketplace, and deals are conducted through an auctioneer.

In

the pristine world of perfect competition, it doesn’t matter whether there isa lack of coincidence of wants between any two people, because people don’t
trade in pairs.

Rather, everyone trades with the auctioneer, who ensuresthat supply matches demand.

In such a world, money isn’t needed, because the3economic machine runs without frictions.

To put this in historical context, the core paradigm in economics isgeneral equilibrium theory -- a theory that can be traced back to Adam Smith,and which has been refined by generations of economists, reaching its fullest
expression in the work of Kenneth Arrow and Gerard Debreu, in the 1950’s.
great deal of modern economics rests on the Arrow-Debreu foundations.

A

Their

framework is justifiably regarded as one of the highest achievements in thescience.

Yet, remarkably, there is no role for money in the Arrow-Debreu

theory of perfect competition.

"So what?", you may ask.
competitive in the first place?

"Whoever thought that markets were perfectly
In the real world, aren’t there lots offrictions that impede trade?"Well, some of the best brains in the profession have succeeded inbuilding physical trading frictions into their models of the market.
theories are ingenious and beautiful.

Their

But, regrettably, models of trading

frictions usually require a lot of special tricks.

With notable exceptions,the models are too rarefied to contribute to mainstream debate.

Moreover, tous, it’s not clear that physical trading frictions are really essential tomonetary theory.

For John Maynard Keynes, the role of money was as central to economic
theory as it was to economic policy.

Money was the branch of the subject

where people held views with religious fervour.
have much in common.

In fact, money and religion

They both concern beliefs about eternity.

The British

put their faith in an infinite sequence:

this pound note is a promise to pay

the bearer on demand another pound note.

Americans are more religious:

this dollar bill it says "In God We Trust".

on

In case God defaults, it iscountersigned by Larry Summers.

Just as religion has sparked some of the worst conflicts in history, so
the subject of money has led to some of the fiercest battles in economics.
John Hicks wrote in the 1930s that " ... it is with peculiar diffidence andeven apprehension that one ventures to open one’s mouth on the subject ofmoney."The battles continued through to the disputes between the Keynesians

4and the Monetarists in the 1970’s and 80’s.

Things have gone suspiciously quiet now.

Monetary theory has gone into

the wings.

In the drama of modern macroeconomics, money plays only a

bit-part.

For most of the actors, monetary theory is merely a side-show

compared to the high drama of value theory.

Nobu and I think this is wrong.

The flow of money and private

securities through the economy is analogous to the flow of blood.

In thebody of the economy, prices are the nervous system, signalling the needs ofdifferent parts of the body.
response to those signals.

Money is the blood that dispatches resources in
No doctor would be content with a model of the

body that ignored the flow of blood.

Value theory and monetary theory need

to be integrated.

We decided early on that the best way to think about money is not tothink about money.
explain.

There is no point in assuming what you are trying toBetter to build a model in which something naturally emerges thatplays the role of money.

We decided to focus on the circulation of private

IOUs.

Let me explain.
money.

A pound note -- cash -- is only one particular kind of

Cash is known as "outside money", because it is issued by thegovernment, and the government is outside the private economic system.

But

there are many other forms of money, that come from inside the system.

Let’s

go back to the dentist.

Suppose I pay her by debit card, instead of cash.

To keep things simple, let’s say that she and I happen to hold accounts atthe same bank.

I find it clearest to suppose that she and I both havenothing in our accounts at the start of today.

When I pay her by debit card,

funds are automatically transferred from my account to hers.

That is, by theend of today, after she’s fixed my teeth, I owe the bank because I’m now
overdrawn, and the bank owes her because her account has a positive balance.
In essence, what’s happened is that I have given the bank one of my IOUs, andthe bank has given the dentist one of its IOUs.

Now:

Why didn’t I just give the dentist one of my IOUs directly?

do we need the bank as a go-between?

The answer may simply be that the5Whydentist doesn’t trust me to repay my debt.
answer.

But there is a more subtle

My dentist may trust me to repay her -- not least because if I don’t

she can always threaten to do something nasty to my teeth next time they needher attention.

But in the meantime she can’t use my IOU for her own

purchases, perhaps because no-one else trusts me, apart from her (and maybe
the bank).

Of course, if she were generally trustworthy, it wouldn’t matter.

She could simply hold on to my IOU, and at any time issue her own IOUs tomake her purchases.

But suppose no-one else trusts her either.

can’t issue her own IOUs.

Then sheNor can she endorse my IOU (like adding asignature to a bill of exchange).

Because if neither of us is trusted byother people, even the combination of her signature and mine won’t be enoughto get my IOU to circulate.

In these circumstances, the only way she can make purchases before therepayment date on my IOU is if she’s paid with the bank’s IOU (and, in
return, the bank holds my IOU).

She can use the bank’s IOU to make purchases

at any time, because, we suppose, everyone trusts the bank.

In short, shegets more benefit from being paid with the bank’s IOU than from being paidwith my IOU.

This brings out a central idea.

The bank’s IOU is used by me and thedentist to lubricate our transaction.

Why?

Because the bank’s IOU canfreely circulate around the economy.

Like blood, it is liquid.

is functionally equivalent to cash.

But, unlike cash, it doesn’t come fromoutside the private system, it comes from inside.
is called "inside money".

In fact, it

For this reason, bank debt

Quantitatively, inside money dwarfs outside money,

by a ratio of around 30:1 in Britain today, depending on how you measure it.
That is, circulating private debt is extremely important, much more important
than cash.

The reason why the dentist and I have to use the bank’s IOU is that,
unlike the bank’s, my IOUs are not liquid.
sticky.

They are illiquid.

They couldn’t pass from my dentist on to anyone else.

definitely not inside money.

They areMy IOUs are

They are just plain IOUs.

Inside money is not a modern invention.
by reading about the medieval economy.

Nobu and I have been inspired

In essence, the issues back then were6

the same as they are today.
were fewer trees.

And it’s easier to see the wood, because there

The economic historian Raymond de Roover’s famous study of

medieval Bruges detailed the importance of banking.
were no debit cards.

In those days, there

Instead, the dentist and I would walk together to thebanker’s premises, and both witness as he wrote in his ledger, deducting frommy account, and adding to the dentist’s.

When I borrow from you, I give you an IOU.
my paper" to you.

To use the jargon, I "issue

Some people’s paper circulates and others’ doesn’t.

paper doesn’t circulate.

Bank paper does.

My

Typically bank paper doesn’tliterally circulate in the form of paper notes, but in the form of ledger
entries or, nowadays, as entries in a computer database.

But there have been

historical episodes when private bank paper has circulated as money -- mostnotably during the free banking era in Scotland in the eighteenth and earlynineteenth centuries.

And, as you can see from these pound notes, certain

Scottish banks still issue notes today.

Before I present a formal model of these matters, let me start with alittle three-date example.

[SLIDE 1.]

There are three days to focus on:

today, Monday; tomorrow, Tuesday; and the day after, Wednesday.

Let’s think about someone hypothetical called Ian.

This morning, Ian

woke up with a great idea for an investment project.

Draw the project likean aeroplane taking off.

It’s not going to come

Ian’s project is long-term.

to fruition tomorrow, but in two days time, on Wednesday.
lands.

Two days may not sound very long-term to you.

days, then think of years or decades.

The aeroplane

If you don’t like

Assuming Ian’s project is a good one,it should land on Wednesday with more funds on board than when it takes off
today.

Unfortunately, Ian doesn’t have the funds needed to get the fullproject off the ground.

So who will lend to him?

Perhaps Jim.

have funds today -- one of his projects has just been completed.
is a difficulty.

Jim does
But there

Jim is only willing to lend short-term -- in fact,

overnight -- because he has an idea for another project that he wants tostart tomorrow.

And so he doesn’t want to tie up his funds any longer than

one night, tonight.

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There is thus a lack of coincidence of wants between Ian and Jim, justas there was between me and my dentist.

But whereas between me and mydentist the lack of coincidence of wants was over the types of good being
offered, here it is over time -- the times of giving and receiving.

Today,

Ian wants to borrow long-term, but Jim only wants to lend short-term.

What we are doing in this example is to recast the classic idea of lackof coincidence of wants from the type dimension to the time dimension.

If the world comprised just Ian and Jim, they would be in a pickle.
But there is a third actor in the drama, Kevin.

He has no funds today.

he does have a project that he started yesterday.
out funds tomorrow, Tuesday.

But

And this project will pay

Kevin wants to save those funds until

Wednesday, when his next project starts up.

They form a curious trio.
until Wednesday.

Ian needs funds today, but won’t get any

Jim has funds today, but needs them back tomorrow.

will have funds tomorrow, and won’t need them until Wednesday.
them has a coincidence of wants.

Kevin

No pair of

But collectively they could do business.

The efficient allocation would be for the person whose project is finishingon any given day to hand over funds to the person whose project is starting.
In an Arrow-Debreu world, this would be the outcome: today, the three parties
would each contract, through an auctioneer, to implement the efficient
allocation.

In fact, the Arrow-Debreu market need open only once, today,

Monday.

If you’re not keen on the idea of a centralized auction, then thinkinstead of a decentralized marketplace today where people write bilateralcontracts.

Kevin contracts to deliver to Jim tomorrow.

pays funds to Kevin today.

Kevin uses these funds to pay for a contract from

Ian promising to deliver on Wednesday.
agreed on today.
Wednesday.

In exchange, Jim

Both these deals are bilateral, andThere is no need for more deals to be struck tomorrow or on

The marketplace doesn’t need to reopen.

In particular, there isno need for Ian’s paper to change hands: Ian borrows from Kevin today, and hepays Kevin back on Wednesday.

8However, there may be a problem.
contracts?

Who is going to enforce these

Although today Ian may promise to hand over funds on Wednesday,

can he be trusted to do so?

Is his promise credible?

And can Kevin betrusted to deliver tomorrow?

They certainly look an untrustworthy bunch.

Notice that the question of trust arises so starkly in this example
because we have switched from the type dimension to the time dimension.

The

crucial twist that time introduces is that if I borrow from you today andthen, later on, I fail to repay you, at that point you can’t undo the initial
loan.

Time is irreversible.

In the 1920’s the Cambridge mathematicalastronomer Arthur Eddington coined the phrase "time’s arrow".

Well, giventhat time’s arrow can’t fly backwards, in economic relationships the questionof trust is critical.

Surprisingly, in Arrow-Debreu the time dimension is treated on a parwith the type dimension.

Trust is ignored.

Implicitly, it is assumed either

that all economic agents are entirely trustworthy, or that the auctioneer canwield a stick that is so big no-one dare renege on a promise.

Nobu and I think that factoring in a lack of trust -- placing alimitation on the degree of commitment -- is of primary importance.

Inparticular, we think that it is the right starting point for a theory ofmoney.

Hence the title of this evening’s lecture: "Evil is the Root of all

Money".

Evil is a strong word.

You may find the moral category too severe forsomething as mild as breaking a promise.

In which case, you may want tochange the title to "Distrust is the Root of all Money".

But that wouldn’t

have quite the same ring.

To get back to Ian, Jim, and Kevin.

If they can’t trust each other,and there are no mechanisms available to enforce promises, then they aredoomed to autarky.
can.

That is, each will have to do his own thing, as best he

Ian will have to scale down his project if he can’t borrow today.

will stuff his funds under his proverbial mattress overnight tonight.
Kevin will stuff his funds under his mattress tomorrow night.
highly inefficient.

Jim
And

All this is

Funds shouldn’t be stuffed under mattresses, they should

9be put to good use.

Is there any remedy to this sorry state of affairs?

Well, even though

they don’t trust each other, there may be a mechanism to enforce promises.

Remember that Ian is starting a new investment project today.
reasonably suppose that his project has assets.

We might

But assets can be mortgaged!

Although Ian personally can’t be trusted, he can offer the assets as
collateral.

So he may, after all, be able to commit to pay out at least partof his Wednesday return, by issuing paper secured against the assets.
important distinction here is between human and physical capital.

The

Ian’s

human capital is inalienable, but his physical capital can be seized in theevent of default.
self-financing.

This makes his pledge credible.

The project is in part

Ian can borrow today to finance a bigger project.

What about Kevin and Jim?

Can they also borrow today?

Presumably not.

For Kevin, it may be too late to borrow against tomorrow’s return.

Yesterday

he may have borrowed as much as could, to invest in a bigger project, and hehas no spare collateral today.

As for Jim, his next project doesn’t start

until tomorrow, and people may be unable to "pre-mortgage" their future
projects.

Let’s agree that only Ian can issue paper today, pledging part of his
Wednesday return.

Think of it as long-term paper, given that it doesn’tmature until two days time.

The question is:

How might Ian’s paper help the three of them to dobusiness with each other?

On the face of it, it doesn’t help.

Jim doesn’twant to hold the paper, because he wants to be repaid tomorrow, and can’t
wait until Wednesday.

And Kevin can’t buy the paper today, because he hasn’t

got any funds readily available and he can’t borrow.

That is, even though

Ian can issue paper, there remains the problem that no pair of them has acoincidence of wants in dated goods.

But there is solution.

Suppose Ian’s paper circulates -- from Ian, toJim, to Kevin, and finally back to Ian.
other, as follows.

Then they can do business with eachToday, Ian borrows from Jim.

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That is, Ian sells hispaper to Jim -- even though Jim doesn’t really want to hold an IOU promising
to repay on Wednesday.

Never mind.

sell the paper on to Kevin.

Because when tomorrow comes, Jim can

Kevin is happy to buy this "second-hand" paper

because he wants to save over tomorrow night.
paper to Ian, who redeems the IOU.

On Wednesday, Kevin takes the

It is important to see that, although Ian

borrows from Jim, Ian repays Kevin.

Taken together, the two short valley-shaped lines represent the journeytaken by Ian’s paper.

They’re drawn in red, to remind us of the metaphor of

the circulation of blood.

Ian’s paper provides the economy with liquidity, the means ofshort-term saving: Jim uses it to save overnight tonight, and Kevin uses it
to save overnight tomorrow night.
money.

The paper is functionally equivalent to

Jim buys it today not because of its maturity value but because of

its exchange value.
the back door.

Notice how we have arrived at a theory of money throughWe haven’t explained money by assuming money.

Instead, we

have shown how this little economy can work well if private debt circulates,
serving as inside money.

Another way to think about this is to use the language of commitment.
In general terms, what we have shown is that if two people want to transact
who don’t trust each other -- who are unable to commit -- then they can makeuse of a third party’s ability to commit.
acts as a lubricant to the transaction.
party" to Kevin and Jim.
tomorrow.

No matter.

The third party’s commitment power
In our example, Ian is the "third

Today, Kevin can’t commit to deliver to Jim

doesn’t need to commit.

Because, thanks to Ian’s commitment power, Kevin
When tomorrow arrives, Kevin simply engages in a

spot transaction.

Roughly speaking, we might say that Ian is acting as a banker to Kevinand Jim.

Deep down, of course, Ian is no different from the other two.

The

only reason why he can act as a banker is that today he has spare collateral.

I want to draw out two central ideas from this example.

First, since

Ian supplies the economy with money, the tighter is Ian’s borrowing
constraint, the more likely there is to be a shortage of liquidity.

11

See theparadox:

Although it is Ian who is doing the borrowing, nevertheless he is

the one who is supplying the economy with money.

That’s the peculiar natureof inside money -- someone’s debt circulates.

Second, for Ian’s paper to act as money, resale must be possible.
paper must be negotiable.

The

It is not enough that Ian can work within his

borrowing constraint to sell his paper today, to Jim.

It must also be

possible for Jim to resell the paper tomorrow, to Kevin.

Unlike inArrow-Debreu, the market must open twice: for the initial sale today, and forthe resale tomorrow.

Let me put this second idea another way.

For Ian’s paper to circulate

as inside money, he must be able to make not merely a bilateral commitment to
the initial purchaser (Jim), but a multilateral commitment to any subsequentbearer of the paper (Kevin).

The distinction between bilateral and multilateral commitment is so
important to us that I’d like to step away from the example for a few
minutes.

It seems clear to us that multilateral commitment is a lot moredemanding than bilateral commitment.

And this has implications for whichkinds of paper can circulate, and which can’t.

Start with private debt.

I can borrow from Nobu, given our closeworking relationship, but he would have difficulty passing my debt on to athird party.

Earlier I gave the example of my dentist, who would be unable

to use my IOUs for her own purchases.

More generally, when a supplier extends trade credit to her customers,
she has special leverage over them because they will need to buy more fromher in the future.

In practice, suppliers have difficulty offloading thiskind of debt: it’s not easy selling trade credit to a third party at a fair
price.

When a bank extends overdrafts to its customers, it too has special
leverage over them because they need to keep the bank sweet for the future.

12

Banks have difficulty reselling this kind of debt.

And the problem isexacerbated by the problem of asymmetric information.

The bank has a goodidea which of its customers are safe, and which dubious.
is private.

But this knowledge

In the secondary market, it’s in the bank’s interest to resell

off what it knows are the bad loans.

Potential buyers are aware of this, andmay be wary of buying -- to the point that the market can collapse.

In our written paper, we tell a different kind of story to rationalise
why paper may not resaleable.

Our story is one of moral hazard.

When anentrepreneur issues paper secured against a project, he gives the initialcreditor some control over access to the project.

Now suppose the creditor

were planning to resell the paper before the project matures.

Then she andthe entrepreneur could collude to strip the project, leaving just a shellthat delivers no output, but which cannot be distinguished from an intact
project by outsiders.

Aware of this possibility, no-one will be willing to

buy the paper in the secondary market.

Whatever the story -- be it special leverage, adverse selection, or
moral hazard -- the conclusion is broadly the same.
possible for an initial creditor to resell paper.
take a long time to resell.

Namely:it may not be

Or perhaps the paper may

And even if there is an active secondary market,

the price may not reflect the true value of the paper to the initialcreditor.

In this evening’s lecture, I want to consider just the two extremes.
Either paper can be resold -- it’s liquid, and can circulate.
resold -- it’s illiquid, and can’t circulate.

Or it can’t be

In tomorrow evening’s lecture,

we will look at intermediate cases, where paper is partially resaleable.

Incidentally, in our example, if Ian’s paper couldn’t be resold, thenthere would be no inside money and trade would completely break down.
three of them would be back to autarky.
that bleak.

The

In general, the outcome need not be

But to achieve efficiency, it’s clear that the circulation of

inside money is crucial.

Before I turn to the full model, let me stress again the two ideas thatcame out of this example.

First, any constraint on Ian’s ability to borrow

13today matters, because it is he who supplies the economy with liquidity.
Second, any constraint on Jim’s ability to resell tomorrow matters, because
unless Ian’s paper circulates it cannot act as money.

These two potential constraints need to be thought about separately.
The first constraint, a borrowing constraint, has received attention in themacroeconomics literature.

Any number of moral hazard stories can be invoked

to rationalise why people face borrowing constraints.

The second constraint,a resaleability constraint, has received much less attention in the formal
literature, but we think is just as important.

In the full model, it is interesting to see how these two constraints
feed into each another.

On the one hand, remember that in this three-dateexample if there were no borrowing constraints, resaleability wouldn’t matter-- just as in Arrow-Debreu, where, because people never renege on theirpromises, paper doesn’t need to circulate.

More generally, we’ll see thateven though there may be less than full bilateral commitment, if there isenough, then multilateral commitment isn’t needed; the economy works wellwithout inside money.

On the other hand, we’ll also see that if paper does circulate as money
because there are no resaleability constraints, then the economy can work
well even though people may not be able to borrow very much.

A little

multilateral commitment goes a long way.

We’ve spent a long time on the three-date example.
are 90% of the way to the full model.

Here it is.

But fortunately we[SLIDE 2.]

Spot the differences between this figure and the last.

First, there isan infinite time horizon, because I want to consider an economy in steadystate.

There is one homogeneous good at each date.

i.e. stuffed under a mattress.

The good can be stored,

I’ve made every Sunday a day of rest.

What

you see in front of you, then, is a typical six-day working week.

Now there are many Ians, many Jims, and many Kevins.
a continuum of each, with total measure 3.

What a terrifying thought.

economy is competitive: there are no trading frictions.

14

In fact, there is
TheActually, the names here are arbitrary, because the entire population
is homogeneous.

Everyone can choose when to start their production cycle.

We focus on the symmetric equilibrium where start-times are staggered evenly.
Each investment project takes three days, from start to finish inclusive -i.e. two nights.

No-one can operate overlapping projects.

There is no uncertainty, either in the aggegrate or at the individuallevel.

We hope that one of the strengths of the model is that it can be used

to discuss money and liquidity in a deterministic setting.

We have come tothink that money and liquidity may not have anything inherently to do withuncertainty.

Rather, they are to do with the twin constraints -- borrowing

and resaleability.

However, there is a serious downside to applying Occam’s razor to get
rid of uncertainty: one cannot sensibly talk about business cycles.

In caseyou feel put off by the stylised nature of today’s model, let me reassurethat in tomorrow’s lecture I will present a fully stochastic model which canbe used to think about liquidity and monetary policy in the presence ofshocks.

How should we model the crucial borrowing and resaleability
constraints?

Start with the borrowing constraint.

Remember the idea is that someone-- let’s call him an entrepreneur -- borrows to finance a new project by
issuing paper secured against the project’s assets.
collateral.

The assets serve as

That is, if the entrepreneur defaults ex post, then his creditor

can seize the assets and liquidate them.

But without the entrepreneur’s

specific human capital, the return from liquidated assets will be lower -let’s say only a fraction qof what it would have been had the assets not1been seized. In effect, the creditor has an outside option worth q times
1the "inside return".

Now suppose the entrepreneur can always push the creditor’s payoff down
to this outside option -- no matter what formal contract has been written.
Then, ex ante, the entrepreneur can’t credibly promise to repay more than a15fraction q

1of the project return.

[SLIDE 3.]______________________________________________________________||||q= fraction of a project’s return that can be mortgaged,| 1||
by selling paper at the time of investment||______________________________________________________________|

We assume that people cannot raise funds at any other time, and cannot
mortgage future projects.

Because production takes two nights, the paper will mature two days
after it has been issued.

This choice of time horizon is deliberate.

It isthe shortest horizon we can get away with in order to model liquidity.

If

production took only one night, paper would mature the day after it isissued, and the question of resaleability wouldn’t arise.
taking two nights, we can ask:-- i.e. on the middle day?

With production

Can paper be resold when it is "middle-aged"

We want to consider both possibilities.

Let q

2

be an index of resaleability.

______________________________________________________________|||& 1 if paper can be resold the day after investment || q2 = {||7 0 if paper cannot be resold||______________________________________________________________|

If q

2

equals 1, paper can be resold.

So:

If q

2

equals 0, paper can’t be resold.

q1 corresponds to the borrowing constraint; and q2 corresponds to

the resaleability constraint.

They are the heart of the model.

By the way,

the mnemonic here is that the subscript 1 on q
paper, and the subscript 2 on q

2

denotes the initial sale of1denotes the resale, a day later.

The rest of the model is quite standard.

[SLIDE 4.]

We assume thateveryone consumes every day, has a logarithmic utility function, and a common

16

discount factor b:

8
S
s=0

bs log ct+s

where 0 < b < 1.

Also, the cost of a project is strictly convex in the output y.

Per capita:

C(y), the cost of producing y_lwhere l > 1.

y

We like to think of this as an economy populated by lots of fast-moving"ants" -- ants called Ian, Jim and Kevin, I guess.
discount factor b as being close to 1.

So we think of theAlso, we think of the technology as

having close to constant returns, so that l is close to 1 too.

In whatfollows, when I say "approximately", I refer to the case where b and l areboth close to 1.

To provide a benchmark, let’s look at a first-best allocation in steadystate.

[SLIDE 5.]

Productive efficiency requires that the marginal cost ofinvestment equals the discounted marginal return.

Since production takes twonights, this means that, per capita, the efficient level of output, y*,satisfies:C’(y*)=

b2.

Also in the first-best, consumption is perfectly smoothed.

That is, everyone

has the same per capita consumption, c* say, irrespective of what point they
are in their individual production cycles.

c*=c* is given by[y* - C(y*)]/3.

17

As I promised, we want to use this model to see how the borrowing
constraint and the resaleability constraint feed into each other.

To do so,

let’s start with the case where paper can be resold, i.e. where q

equals 1.

[SLIDE 6.]

2

Just as in our earlier three-date example, resaleable paper

provides the economy with liquidity.

The paper acts as inside money.

Take one of the Ians, on a Monday.

He borrows long-term -- by selling

new paper to some Jim in the competitive market.

The next day, Tuesday, Jim

resells Ian’s paper, which is now second-hand, to some Kevin, in the same
paper market.

Notice that because there is no uncertainty, new andsecond-hand paper are perfect substitutes as means of short-term saving.

The

next day, Wednesday, Kevin takes the paper back to Ian, who redeems it.

Eachday, the three of them rotate roles.
filled with red lines.

As you can see, the whole diagram is

Think of this as a "red economy", because the paper

is like blood: it is red and circulates.

It is inside money.

Thanks to money, the first-best can be attained relatively easily.
[SLIDE 7.]

Proposition 1 (red economy)_____________
If paper is resaleable (q
iff q

1

= 1), then the first-best is attained2
is greater than approximately 1/3.

The reason why paper is resaleable -- why q

equals 1 -- is that agents2
are able to make multilateral commitments to repay any bearer of their paper.
Proposition 1 confirms something I said earlier:commitment -- q1

as low as 1/3 -- goes a long way.

A little multilateralIt’s enough to attainfirst-best.

However, if there is no multilateral commitment, if paper can’t be
resold, then matters are very different.

We saw before that the three-dateexample collapsed to autarky if Jim couldn’t resell Ian’s paper to Kevin.

18

Nobu and I thought that the same would be true in this stationarymodel.

After all, there appears to be a complete lack of coincidence ofwants in dated goods: borrowers want to borrow long-term, over two nights;
whilst savers want to save short-term, over only one night.

But without

resaleability -- without money -- all deals have to be bilateral.

This iswhy we thought that, in the apparent absence of coincidences of wants, there
could be no gains from trade.

We were wrong!

When q= 0, the infinite-horizon economy doesn’t
2collapse to autarky. Instead, something much more interesting happens.
[SLIDE 8.]

Even though paper is now illiquid, the economy finds a way ofcreating coincidences of wants.
Jims.

What happens is this.

On a Monday he lends to some Ian.

Consider one of theThat is, Ian issues an IOU, which

Jim has to hold through to Wednesday because it is illiquid and can’t be
resold on Tuesday.

On Wednesday, when the debt is due, Ian repays Jim.

promptly lends to some Kevin, who is starting a project.
issues an IOU, which Jim holds through to Friday.
lines represent Ian and Kevin’s paper.
illiquid paper.

That is, Kevin

The two long valley-shaped

They’re drawn in blue, to denote

On Friday, when Kevin’s debt is due, he repays Jim, who can

now invest in his own project!
Monday.

Jim

Jim’s project completes on the following

In effect, Jim’s Monday/Wednesday/Friday/Monday budgets are linked-- by holding blue paper (twice) and investing (on Fridays).

It is important to realise that Jim doesn’t miss his Tuesday investment
opportunity -- because his Saturday/Tuesday/Thursday/Saturday budgets arelinked too.

However, there is no link in the budgets of consecutive days.

Think of two parallel turnpikes, with no cross roads to join them.

We could go on and fill up the diagram with blue lines like these.
they say in cookery programmes, here’s one I prepared earlier.

As[SLIDE 9.]

In this economy, paper is illiquid and so cannot circulate, but theeconomy is making the very best of a bad job.

Let’s call this a "blueeconomy", to distinguish it from the earlier "red economy" where paper was
liquid and could circulate.
lubricant.

The blue economy has no inside money to act as a

And yet, ingeniously, the economy manages to create coincidences19

of wants, where savers as well as borrowers are willing to use the illiquid
paper.

I must stress that the ingenuity here is not ours.

that is ingenious.

It is the economy

The economy succeeds in finding gains from trade.

I

think this is a great example of Adam Smith’s invisible hand at work.

But there is a problem.
economy.

Just compare the blue economy with the red

You can tell at a glance that the blue economy uses much more paper

than the red.

If you think about it, the demand for paper in the blue

economy is four times as great as it is in the red economy.

This puts a greater strain on the paper market.

For the economy to run

efficiently, there has to be a greater supply of paper.
to issue more paper when it is their turn to invest.
higher.

We have the following proposition.

Agents must be able

That is, q1

must be[SLIDE 10.]

Proposition 2 (blue economy)_____________
If paper cannot be resold (q
iff q

1

= 0), then the first-best is attained2
is greater than approximately 2/3.

Given that the demand for paper is four times greater in the blue economy
than in the red, you may be puzzled as to why the critical value of q
doubles.

The answer is that, ceteris paribus, doubling q

1

only
1
simultaneously

doubles the supply of paper and halves the demand.
It’s interesting to note that the critical threshold for q
Proposition 2 is strictly less than 1.

in1
It is approximately 2/3. Thisconfirms something else I said earlier:

Even though there may be less thanfull bilateral commitment, if there is enough, then multilateral commitment
isn’t needed; the economy works well without inside money.
Taken together, Propositions 1 and 2 tell us that when qlies between
1
1/3 and 2/3, the red economy attains the first-best, but the blue economy
doesn’t.

20

What is the general message to take away from this?

Simply that if

paper is less liquid, it is less convenient to use, and the economy needs
more of it.

This increased demand puts greater strain on the paper market.

There may be a shortage of paper.
shortage".

I’d like to adopt the phrase "liquidity

For qlying between 1/3 and 2/3, the blue economy has a1liquidity shortage, but the red economy doesn’t.

There is not time to give details, but my third Proposition lists someof the symptoms of a liquidity shortage in the blue economy.

[SLIDE 11.]

Proposition 3 (blue economy)_____________
Assume q

2

=

0

and q

(paper cannot be resold)
1

<

2/3

(=> liquidity shortage)

Then symptoms of a liquidity shortage include:Q

price of two-period paper>b2(implied one-period rate of return on paper<Qborrowing constraints bind on day of investment

Q

consumption is jagged

1/b)(lowest on day of investment; highest the day before)

Q

investment and output are lower than in first-best

Moreover, the lower is q , the worse are these symptoms
1
For low enough q , there can be inefficient storage, even though1rate of returnon storage

<
.
.
.
.
.
.
.
.

implied one-period
rate of returnon paperliquidity premium

21

The shortage of paper causes the price to be high -- which means thatthe implied rate of return on paper is low.

Agents starting new projects

would like to borrow more at these low rates, but they face binding borrowing
constraints.

The other agents are discouraged from saving.

log-jam in the paper market.
borrowers.

There is thus a

Too few resources are transfered from savers to

As a result, investment is low; and output is low.

Roughly

speaking, the economy runs "too slowly".
These symptoms are worse in an economy with a lower q .
1
For low enough q , savers are being offered such a low
1
return on their illiquid paper holdings that, at the margin, they resort to[SLIDE 12.]

storage, i.e. they stuff their mattresses.

Storage offers an even lower rateof return, but at least has the virtue of being short-term and hence liquid.
Think of the gap between the return on storage and the implied one-period
return on paper as a liquidity premium.
When qlies between 1/3 and 2/3, all these symptoms are experienced by1
the blue economy, but not the red. In other words, we can blame all thesebad things solely on the fact that paper cannot circulate in the blue economy-- that there is no inside money.

Your reaction to all this might be to ask:

"Why doesn’t the blue

economy somewhow create inside money?"Well, one way to create inside money is to add some wealthy agents tothe model.

Let’s add some Scottish lairds, who each own a castle.

doesn’t necessarily produce anything.

A laird

But as long as his castle is publicly

visible, he will be in a position to make multilateral commitment.
issue paper secured against his castle.

He canBecause of the multilateralcommitment, his paper can circulate as inside money -- it is red.

[SLIDE 13.]

Here is an economy where blue paper and a small amount of

red paper coexist.

Consider one of the Jims, on Monday the day he completes

A fraction 1 - qof the project’s output has not been mortgaged.
1
He has a choice about what he does with these unmortgaged funds. Either hea project.

22can follow what one might call a "fast strategy": buy red paper so as to fundinvestment on the next day, Tuesday.

Or he can follow a "slow strategy": buyblue paper twice in succession, so as to fund investment four days later, on
Friday.

When blue and red paper coexist, Jim will mix between buying red andblue paper on Monday.

In order for him to be indifferent between the fast and slow
strategies, blue paper has to offer him a premium over red paper.

That is,the implied interest rate on illiquid blue paper has to be greater than theinterest rate on liquid red paper.

The interest rate differential, theliquidity premium, is the compensation Jim demands for the inconvenience ofholding illiquid paper.

Of course the trick would be to make a profit by buying blue paper andselling red!

Imagine setting up your stall at Carfax, offering to lend to

private people whose IOUs are illiquid.

Since their paper is illiquid, blue,

they have to pay you a relatively high rate of interest.
funds by taking in deposits.

Meantime, you raise

Because you are sitting at your stall all day

and every day, you become quite a public figure, and your IOUs, the paper you
hand to your depositors, is liquid; it’s red.

So you can get away withoffering your depositors a lower rate of interest than you receive from yourdebtors.

You are making a profit, merely by sitting there!

you are?

You are a bank.

Do you know what

You effectively transform blue paper into red.

There is a more direct way you might transform blue paper into red:
you could simply certify it.

That is, you could add your signature

underneath the signature of the issuer -- as happens on a bill of exchange.
Once certified, the paper can circulate, because your signature -- yourguarantee -- is commonly recognized.

As a banker, you don’t necessarily produce anything.
you are on a par with the Scottish lairds.

In this respect,

There is a difference, though.

Whereas the lairds issue red paper secured against their castles, you issue
red paper secured in part against other people’s blue paper.

Unlike thelairds, you have to work a little to earn your profit -- sitting out there in
the cold, rather than ensconced in a castle.

23

We can incorporate banks into the model.
theory of banking.
at Carfax.

Here is a (very!) rudimentary

Dispense with lairds and castles, or people sitting out

Instead, let’s go back to some Ian, starting a project on Monday.

In the blue economy, Ian mortgages a fraction qof his Wednesday output by
1
issuing illiquid paper, paper that cannot be resold on Tuesday. In the blue
economy, Ian can only make a bilateral commitment -- to the initial purchaserof the paper, Jim.

The story is that on Monday night, Ian and Jim could

collude to asset-strip the project.

And, knowing this, no Kevin is willingto buy the paper on Tuesday.

But now suppose Ian can ring-fence his project in a way that limits thepotential for asset-stripping.

By erecting a fence, Ian can turn at least

part of his paper from blue to red.

He is his own bank.

One can think of this fence either literally or metaphorically.
Literally, the cost of fencing is strictly convex in the height of the fence.
The higher it is, the stouter have to be the posts to hold it up.

And thehigher the fence, the greater the fraction of Ian’s paper that is red.

In

general, Ian will therefore choose an interior value of q , the fraction of2
liquid paper that he issues.

That, in the briefest possible terms, is our theory of banking.
theory of fencing.

A

I’ll be returning to fencing again in my final lecture.

The interesting question arises: does a private banking system create
enough liquidity to maximize welfare?
used, the answer is no:

We find that, whenever storage isleft to itself, the banking system is too small.

Given that people store, there is too little fencing:at the margin, thedirect cost to society of erecting taller fences would be outweighed by theindirect benefits of extra liquidity -- in social terms, banks transform too
little blue paper into red.

This is provocative.

But I must add a caveat.

In arriving at ourconclusion, we have used a crude "Modified Golden Rule" welfare criterion.
We haven’t considered transition dynamics, or distributional issues, which
ought to be part of a fully-fledged welfare analysis.
only tentative.

24

So our conclusion isNevertheless, it suggests a role for government, or a central bank, tosupport the banking system.

I’ll return to this theme in tomorrow evening’s

lecture, when I introduce government money and bonds into a stochastic model.

Banks are not the only way of turning blue paper into red.

In May 1970

there was a banking strike in Ireland, which lasted over six months.

It wasfeared that the economy might collapse -- because, without banks, there would
be too little liquidity.

In the event, even though over 80% of the money

supply was frozen, the economy hardly blipped!

Do you know why?

The pub

landlords took over, and started circulating IOUs through their bars.

Thisis a nice illustration of the resilience of an economy, to create alternative
supplies of liquidity.
economy.

Guinness is not only good for you, it’s good for the

A paper on this episode (and two other banking strikes in Ireland)

was published in the Manchester School (March 1978) by Antoin Murphy. As---------- -----Professor Murphy pointed out: "one does not after all serve drink to someone
for years without discovering something of his liquid resources".

We can see the same creativity in medieval times.

From the work of theeconomic historian M.M.Postan, we learn that in the Middle Ages the legal
system threw up obstacles to the transfer of debt.

To use our language, thelegal system artificially prevented blue paper from being red.
happened?

And what

People devised new forms of contract, like the bill of exchange,

to wriggle round the law.

Notice again, just as in the Irish banking strike,the economic drive to create liquidity is hard to stop.

The invisible handat work once again.

In reality, there is every shade of colour between blue and red.

The

approach I will adopt in tomorrow evening’s lecture is to measure liquidity
in terms of the speed with which assets can be resold at a fair price.
Measured this way, private debt is the bluest of blue paper, because
typically it can never be resold.

Trade credit and bank loans are also

fairly blue -- in the sense that suppliers and banks can only resell thiskind of paper at less than the true value.

A stake in a small firm might be resaleable; but to find a buyer would
take time.

So this kind paper is only moderately liquid: think of it as25

purple.

Corporate bonds and equity are examples of fairly red paper: they

can typically be resold quickly, and so are quite liquid.

With the latest innovations, paper that was blue is becoming redder.
Mortages used to be blue, but are now red, thanks to the creation ofmortgage-backed securities.
Royal Bank of Scotland.

I may think that I make mortgage payments to the

But in fact my mortgage has almost certainly been

bundled with lots of other people’s, sliced up in clever ways, and thenresold.

It has probably been resold many times since.

mortgage has become like inside money.

In other words, my

And thanks to new electronic tradingmechanisms, stocks and shares can be sold more quickly than before: they are
now redder.
In this evening’s model, q

was the counterpart to the colour of paper.
2
The higher the value of q , the redder the paper. I am suggesting that2
recent developments in financial markets have pushed up q ’s, and are
2continuing to do so.
There are reasons to suppose that q ’s have gone up too. It is argued
1
that loans can now be more accurately targeted at certain groups ofborrowers.

And, perhaps more importantly, borrowers have more to lose fromcheating.

Credit scoring has become the norm.

If I want to borrow today,

potential lenders don’t consider so much what I want to use the funds for.
Nor do they even consider what collateral I have to offer.
at my credit history, and other aspects of my past life.

Mostly, they look
The reason is thatmuch more information can be stored about my past, which can be used toassess the likelihood of my defaulting.
much more widely available.

Also, crucially, this information is

And that puts a greater premium on mymaintaining my financial reputation.

It’s not that I am inherently any moretrustworthy, but rather that the scope for my getting away with things is
less.

In terms of the model, this means that my qis higher. And so the1
supply of liquidity is higher too -- which, as we have seen, improves thestate of the economy.

Let me end by coming back to where I started: these pound notes.
The reddest paper of all.

Cash.

It earns no interest. (With inflation, it actuallyearns a negative return, but let’s ignore that.)26

In the year 2001, peoplehold cash.

So, we may conclude that, in the current spectrum of interest

rates, zero must be the rate of interest on the reddest paper.
no reason why this should always be true.

But there is

Cash is not a logical necessity.

To see why not, consider this evening’s model.

Cash -- i.e.

non-interest-bearing fiat money -- can circulate alongside inside money.

But

only if the interest rate on red paper drops to zero, which happens if q
low enough.

is1
In other words, fiat money can only augment the aggregate stockof liquidity if there is demand for it.

Fiat money will play a role intomorrow evening’s model.
In the future, as the q ’s and q ’s rise further, so the spectrum of
1
2
interest rates will shift up. Eventually, it may be the case that no-one
will be content to earn zero interest on the reddest of papers.

Fiat money

may disappear, crowded out by ultra-liquid private securities that earninterest.

Before long, I may be using a Merrill Lynch card to pay my dentist

in MicroSoft shares.

The thesis that fiat money may disappear is controversial.
several interesting arguments against it.
too much on the supply of liquidity.

There areFirst, we may be focussing here

As the pace of the modern world

quickens, people need to respond more quickly to opportunities.

To put it

grandly, as the time interval in people’s lives shrinks, the problem offinding coincidences of wants in dated goods becomes more severe.

Our demand

for liquidity may be rising in line with the supply.

Next, our discussion presupposes that (fiat) money and other assets aresubstitute means of saving.
complementary.

It can be argued that in fact money isAfter all, assets such as bonds are promises to pay in money.

This may be the point to bring back the idea that money lubricates trade in
the absence of markets.

We may need to model trading frictions after all.

Finally, cash will always be useful to people who want to conceal theirnefarious activities, like drug dealers, because cash leaves no electronic
trail.

If, in due course, crime turns out to be the only reason why people

hold money, then evil will still be the root of all money, but for different
reasons than the ones I have outlined this evening.

27