A collapse in U.S. stock prices certainly would cause a lot of white knuckles on Wall Street. But what effect would it have on the broader U.S. economy? If Wall Street crashes, does Main Street follow? Not necessarily.

The crisis in Europe has affected the US economy by acting as a drag on our exports, weighing on business and consumer confidence and pressuring US financial markets and institutions.

A meritocracy is a system in which the people who are the luckiest in their health and genetic endowment; luckiest in terms of family support, encouragement and, probably, income; luckiest in their educational and career opportunities; and luckiest in so many other ways difficult to enumerate - these are the folks who reap the largest rewards.

Indeed, in general, healthy investment returns cannot be sustained in a weak economy, and of course it is difficult to save for retirement or other goals without the income from a job.

The lesson of history is that you do not get a sustained economic recovery as long as the financial system is in crisis.

Not all information is beneficial.

I served seven years as the chair of the Princeton economics department where I had responsibility for major policy decisions, such as whether to serve bagels or doughnuts at the department coffee hour.