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Background Information

Where and when did you first begin to study economics?

I was a math and physics major at the University of Chicago. I took my first

economics course in my senior year because I was planning to go to law

school. I did well in the class and the professor encouraged me to go on to

graduate school to study economics. Economics offered some of the same

intellectual appeal as physics – it uses simple mathematical models to understand

how the world works – and in contrast to physics, it was an area of

academic study where I could actually get a job.

In some ways staying at the University of Chicago was attractive because it

had a very exciting economics department but I had already been there for

four years. Even though I had had very little Chicago economics training I

did not think it was a good idea to spend my whole career as a student in one

place, so I started in the PhD programme at MIT. There I met my wife, who

was just visiting for a year from Queens University in Canada. After two

years at MIT we went back to Queens to finish her final year of training in

medicine. That was when I started working on growth. At the end of that year

I transferred to Chicago, where my wife had a fellowship position, and

completed my PhD. I finished my PhD and entered the job market in 1982 –

my thesis is actually dated 1983 because it took me a year to polish it up.

As a student did you find any of your teachers to be particularly influential or

inspirational?

Well, Sam Peltzman was the professor who encouraged me to switch my

career path from law to economics. I shudder to think what my life would

have been like if he hadn’t asked to talk with me after the mid-term and I had

gone on to law school. It is an episode that I try to keep in mind – that

professors can be very influential, and a little bit of attention to your students

as people can make a big difference in their lives.

Besides having saved me from a life in the law, Sam was also an excellent

teacher. He was the first person to show me that you could take very simple

tools – demand curves or indifference curves – and derive surprising insights

about how the world works. Having mentioned Sam, I should also mention

some other very good teachers that I had. Donald McCloskey, now Deirdre

McCloskey, was the second person I had for economics. Donald, like Sam,

took economics very seriously. Together, they gave me an excellent introduction

to the subject. I should also mention that at Chicago, they did not offer

what is known as a ‘principles’ course, the watered-down, mind-numbing

survey course that most universities offer as a first course in economics. At

Chicago, they started right off at the intermediate microeconomics level. So I

had the enormous advantage of starting off with challenging, intellectually

coherent material and first-rate teachers. I was very fortunate.

Later in graduate school, when I was back at Chicago, Bob Lucas and Jose

Scheinkman had a big influence on my style and the way I look at the world.

They set a standard for rigour and discipline – zero tolerance for intellectual

sloppiness – that I have aspired to ever since. But probably the best year of

graduate school was the year I spent at Queens University because I had a lot

of interaction with the faculty there. Normally as a graduate student you do

not really get that much time to sit and talk with members of the faculty as

colleagues. At Queens I had more of that kind of experience. Some of the

people I talked with intensively during that year – Russell Davidson and

James McKinnon – are terrific economists and had a big effect on my career.

Development of Macroeconomics

Are there any particular papers or books that you would identify as having a

major influence on the development of macroeconomics?

For me that’s too broad a question. I could list all the usual suspects, people

like Keynes, and so on. I’d be more comfortable describing the contributions

that have influenced my own work.

Tell us about the influences on your own research interests.

Bob Lucas brought a style to macroeconomics that had a big impact on a

whole generation of people, including me. There are several papers that

exemplify this style. One is his 1972 Journal of Economic Theory paper on

‘Expectations and the Neutrality of Money’. Another would be his 1978

Econometrica paper ‘Asset Prices in an Exchange Economy’. But his 1971

Econometrica paper, ‘Investment under Uncertainty,’ written with Edward

Prescott, is probably the best example because it really brought to the forefront

and crystallized for macroeconomists the connection between what we

did in macroeconomics and what the rest of the profession had been doing in

general equilibrium theory. In that paper Lucas and Prescott used the connection

between solving optimization problems and equilibria that has become

such a powerful tool in modern macroeconomics. That 1971 paper builds on

the work of people like Cass [1965] and Koopmans [1965], who had been

working in growth theory, and this basic approach for characterizing dynamic

equilibria can be traced all the way back to Frank Ramsey’s [1928] paper.

Still, Lucas and Prescott took this approach much further into the core of

macroeconomics. If all you have seen is the theory of investment as devel676

oped by the macro modellers and presented by the macro textbook writers,

this paper is like a flash of lighting in the night that suddenly shows you

where you are in a much bigger landscape.

You mentioned the influence of Bob Lucas’s work. What do you think has

been the lasting impact of his work, particularly the work he carried out in

the 1970s for which he was awarded the Nobel Prize?

I think the deeper impact of Lucas’s contributions has been on the methodology

of the profession. He took general equilibrium theory and operationalized

it so that macroeconomists could calculate and characterize the behaviour of

the whole economy. Just as Peltzman and McCloskey took intermediate

microeconomics seriously, Lucas took general equilibrium theory seriously.

Many of the people doing general equilibrium theory for a living did not

really seem to believe in what they were doing. They gave the impression that

it was a kind of mathematical game. Economists working in trade and growth

had shown us how we could use general equilibrium models, but they were

not ready to bring dynamics and uncertainty into the analysis. It was economists

working first in finance, then in macroeconomics, who took the theory

seriously and showed economists that fully specified dynamic models with

uncertainty had real implications about the world. A very important result of

that methodological shift was a much greater focus on, and a much deeper

understanding of, the role of expectations. But this is only part of the deeper

methodological innovation. You still wouldn’t know it from reading textbooks,

but to research professionals, it finally is clear that you can’t think

about the aggregate economy using a big supply curve and a big demand

curve.

One of the ironies in this revolution in thinking is that the two people who

did the most to bring it about, Lucas and Robert Solow, ended up at swords’

points about the substantive conclusions that this methodology had for macroeconomic

policy. Solow’s work has also had a huge impact on the profession,

pushing us in the same direction. His work on growth also persuaded economists

to take simple general equilibrium models seriously. Many people

recognize the differences between Lucas and Solow over macro policy questions,

but fail to appreciate the strong complementarity between their work at

the methodological level. If Joan Robinson had won the day and banished the

concept of a production function from professional discourse, Lucas and

Prescott could never have written ‘Investment under Uncertainty’.

During the 1980s, the real business cycle approach to aggregate fluctuations

developed in parallel with new growth theory. How do you view that work, in

particular the way it has sought to integrate the analysis of fluctuations and

growth?

A lot of the progress in economics still comes from building new tools that

help us understand very complicated systems. As a formal or mathematical

science, economics is still very young. You might say it is still in early

adolescence. Remember, at the same time that Einstein was working out the

theory of general relativity in physics, economists were still talking to each

other using ambiguous words and crude diagrams.

To see where real business cycle theory fits in, you have to look not just at

its substance and conclusions but also at how it affected the methodological

trajectory I was talking about before. You can think of a hierarchy of general

equilibrium models – that is, models of the whole economy. At the top you

have models of perfect competition, which are Pareto-optimal so that you can

solve a maximization problem and immediately calculate the behaviour of

the economy. Then, at the next level down, you have a variety of models with

some kind of imperfection – external effects, taxes, nominal money, or some

kind of non-convexity. In many cases you can find a way to use some of the

same maximization tools to study those dynamic models even though their

equilibria are not Pareto-optimal. This is what Lucas did in his 1972 paper

‘Expectations and the Neutrality of Money’. Formally it is like an external

effect in that model. It is also what I did in my first paper on growth.

The real business cycle guys went one step further than Lucas or I did in

trying to simplify the analysis of aggregate economies. They said, ‘We can go

all the way with pure perfect competition and pure Pareto optimality. We can

even model business cycles this way. Doing so simplifies the analysis tremendously

and we can learn a lot when we do it.’ My personal view – and

increasingly the view of many of the people like Bob King, who worked in

this area – is that at a substantive level real business cycle theory simplifies

too much. It excludes too many elements that you need to understand business

cycles. This doesn’t mean that the initial work was bad. It just means

that we are now ready to go on to the next stage and bring back in things like

predetermined nominal prices. Methodologically this work helped us refine

our tools so we’ll do a better job of understanding predetermined prices when

we bring them back into the model.

We frequently make progress in economics by seeming to take a step backwards.

We assume away real problems that people have been working on in

vague and confused ways, strip things down to their bare essentials, and get a

better handle on the essentials using some new tools. Then we bring the

complications back in. This is what Solow was doing, and what drove Robinson

to distraction, when he modelled the production structure of an economy using

an aggregate production function. Later we brought back many of those complications

– irreversible investment, limited ex post substitution possibilities,

and so on – back into the model. The real business cycle theorists did the same

kind of thing, and during the simplification phase, they also made people mad.