But it could happen maybe one out of 100 times. In the U.S., stocks have never fallen behind inflation over long periods. Jeremy Siegel, a finance professor at the University of Pennsylvania's Wharton School, has examined U.S. stock-market performance going back to 1802. That, however, doesn't mean stocks always whip inflation. Results for other national markets, especially those that have suffered greater political turmoil, wouldn't be nearly so impressive.
Opportunity knocks Forget about losing money in stocks over long periods.
It's the risk that you would have done better in the bank or with bonds. It's an opportunity-cost issue. This century, U.S. bonds have never beaten U.S. stocks over a 30-year period. But don't take that as conclusive evidence, says William Reichenstein, an investments professor at Baylor University. Bonds may not have beaten stocks over a 30-year period in the 20th century.