A "formalization of Summer's hypothesis":
Larry Summers on Fear and Greed, macromania: I used to think that Larry Summers was a reasonable sort of fellow. By here is some evidence proving that spending too much time in administration and politics can rot even the best mind; see White House: Greed Will Help. Here are some quotes:
"In the past few years, we’ve seen too much greed and too little fear; too much spending and not enough saving; too much borrowing and not enough worrying," Summers said Friday in a speech to the Brookings Institution. "Today, however, our problem is exactly the opposite."
Borrowing, you see, is evidently linked to greed; especially if one borrows too much. I am reminded of university students who mindlessly accumulate too much student debt. The greedy bastards. Or of poor people mindlessly borrowing to finance a home purchase. The greedy SOBs. There is too much borrowing; too much spending; there is too much greed.
Saving, on the other hand, is evidently linked to fear. Fear is a virtue (as in the fear of God). As when all those virtuous savers bid up the NASDAQ to 5000. Whoops; this doesn't sound right. Perhaps he means saving in virtuous assets, like government treasuries (backed by virtuous/coercive taxation; rather than the prospect of future cash flow from a successful enterprise). Yes, fear is a virtue...unless there is too much fear. Then fear is bad.
To summarize then: greed is vice; fear is a virtue. Unless there is too much fear, which is not a virtue. Not enough greed is a virtue; but not a good virtue...which is to say it is a vice. I am getting confused. Let me consult the article again.
"While greed is no virtue, entrepreneurship and the search for opportunity is what we need today."
OK, this clears things up. Make no mistake: greed is no virtue. But we do need more of it at a time like this.
So to sum up, greed (borrowing) is bad and fear (saving) is bad (unless there is not enough of either). In the world economy (a closed system), we know that borrowing = saving. And this proves that greed is always balanced by fear. Wait a second, I am confused again. Perhaps what we need is a "new generation" IS-PC-TR like model to help policymakers confront the difficult economic choices they face in balancing fear and greed.
Assume that the policymaker has a quadratic loss function in deviations of actual fear and greed around some socially optimal level of fear and greed (we will let Woodford provide the microfoundations for this social welfare function). Accordingly, let us write this loss function as,
L(t) = 0.5(f(t) - f)^(1/2) + 0.5(g(t) - g)^(1/2)
Here, (f,g) are the socially optimal levels of fear and greed. f(t) and g(t) are the prevailing levels of fear and greed at date t. The policymaker wishes to minimize the fluctuations in fear and greed around their socially optimal levels.
We need more restrictions. Let's see. It seems natural to suppose that fear is influenced in some manner by endogenous variables and an exogenous shock; let's say
f(t) = a*f(t-1) - b*y(t) + e(t)
where y(t) is the output gap; and e(t) is the shock (like a "fear" markup shock in New Keynesian models).
Greed, on the other hand, is influenced by the interest rate and exogenous factors; e.g.,
g(t) = c*g(t-1) - d*r(t) + u(t)
where r(t) is the interest rate, set by monetary policy. Lowering r(t), the way Greenspan did, results in an increase in greed. Seems right.
Now, the policymaker wishes to choose an interest rate rule that minimizes the loss function, given the stochastic processes (estimated as the residuals from a mindless OLS or VAR) governing the fear and greed shocks.
Yes, I can see how the New Keynesian model, so widely used by central banks to justify the policies they follow, will no doubt be replaced by my formalization of Summer's hypothesis. The implications for policy design are likely to prove equally enlightening. Anyone care to coauthor this paper with me? Fame (or notoriety) is virtually guaranteed!