Wednesday, February 17, 2010

On Prof. Stiglitz once again

The new IB economics syllabus will include bits fom the economics of information literature which a owes vey much to Joseph Stiglitz.

As I mentioned in one of my sections a few days ago, the latest issue of the IMF magazine 'Finance and Development' has a very interesting and readable presentation of Stiglitz and his work that you should read.
Realizing Stiglitz’s potential, his professors encouraged him to leave Amherst after his third year and start graduate work elsewhere; they were nevertheless devastated to see him go. “Frankly, seeing Stiglitz leave is like watching the disappearance of one’s right arm,” one of them wrote. The Massachusetts Institute of Technology (MIT), however, was overjoyed to get him as a student. The institution’s admissions committee sent his information to the economics department and asked what the amount of his stipend should be, listing choices ranging from no stipend to $12,000. The professor assessing Stiglitz’s application scribbled on the folder: “Offer him Department Head’s salary.”

A common theme in his papers is the difficulty in getting markets to function properly when information is costly to acquire or when the parties involved in a transaction are not equally informed.

In a 1981 paper with Andrew Weiss, Stiglitz gave a powerful demonstration of how credit markets could malfunction when this was the case. In the textbook model of credit markets, interest rates work to bring about balance between supply and demand; if there is too much demand for credit relative to supply, interest rates rise to cut off the demand of some of the borrowers. But what if lenders don’t know which of their borrowers will work hard at their projects and repay the loan and which are going to shirk and simply hope that good fortune will enable them to pay off the loan? If there is excess demand for credit, raising the interest rate discourages the hard-working borrowers but not those who are intending to take a gamble with the loan. So, far from restoring balance between supply and demand as in the textbook model, the rise in the interest rate actually ends up tilting the composition of borrowers toward the undesirable type. Nalebuff says the Stiglitz-Weiss paper shows that “who you end up lending money to or what they do with that loan changes with the interest rate you charge . . . . Or, as Groucho Marx might have said: ‘I wouldn’t want to lend money to anyone who would borrow at that interest rate.’ ” The Stiglitz-Weiss paper helped develop a more realistic description of credit markets by showing why lenders might engage in credit rationing (i.e., limit the volume of loans) rather than raise the interest rate. In other papers, Stiglitz showed that such information gaps could also plague labor markets. In the textbook model, the wage rate is the lever that eliminates unemployment by moving up or down as needed to balance out the demand and supply of labor. But, just as in the credit market, there are informational deficiencies. Employers often lack accurate information about which of their workers will give the proverbial 110 percent to their job and which are inclined to shirk. They could of course monitor their employees to determine who’s been working hard and who’s been merely saying so. But such monitoring is costly in terms of the employer’s time and can lower employee morale.

Employers, Stiglitz argued, are therefore likely to use the wage rate as a tool to separate workers from shirkers. They may offer a wage higher than the going market rate as an incentive to induce hard work from those who are willing and able to supply it. Paying a wage higher than the competition means that the good workers have something to lose if their jobs are terminated; they thus have an incentive to work hard. But with wages set above a competitive level, the wage rate no longer acts a lever to eliminate unemployment. In fact, as Stiglitz demonstrated in a 1984 paper with Carl Shapiro, unemployment is necessary as a “disciplining device” to keep workers from shirking.

Stiglitz also questioned how well stock markets could work when their information was costly to acquire. A tenet of the textbook model of stock markets is that stock prices accurately reflect all publicly available information. But in a 1980 paper with Sandy Grossman, Stiglitz presented a paradox. If prices reflect all the market information perfectly, then no one should bother to collect information because they can get it for free from the prices. But if no one bothers to collect information, then prices reveal no information. “The paradox lays the basis for the argument that imperfect information is likely to be the rule, rather than the exception,” says Nalebuff.

Read the whole article here.

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