## Economists Not Understanding Their Own Models Department

Paul Krugman:

Ricardian Confusions (Wonkish): Via Mark Thoma, Antonio Fatas criticizes the chief economist of the World Bank for getting the implications of Ricardian equivalence for fiscal policy all wrong. I’ve been on this case for a while. Let me repost most of it:

It’s one thing to have an argument about whether consumers are perfectly rational and have perfect access to the capital markets; it’s another to have the big advocates of all that perfection not understand the implications of their own model.

So let me try this one more time.

Here’s what we agree on: if consumers have perfect foresight, live forever, have perfect access to capital markets, etc., then they will take into account the expected future burden of taxes to pay for government spending. If the government introduces a new program that will spend $100 billion a year forever, then taxes must ultimately go up by the present-value equivalent of$100 billion forever. Assume that consumers want to reduce consumption by the same amount every year to offset this tax burden; then consumer spending will fall by $100 billion per year to compensate, wiping out any expansionary effect of the government spending. But suppose that the increase in government spending is temporary, not permanent — that it will increase spending by$100 billion per year for only 1 or 2 years, not forever. This clearly implies a lower future tax burden than $100 billion a year forever, and therefore implies a fall in consumer spending of less than$100 billion per year. So the spending program IS expansionary in this case, EVEN IF you have full Ricardian equivalence.

Is that explanation clear enough to get through? Is there anybody out there?

Apparently not — at least not at the World Bank.