Cordaro's prediction echoes the view of a number of economists and market watchers that stock returns should fall.
Why? Cordaro says that the big gains of the past were "the result of a repricing that you can't figure will keep happening." Investors, the argument goes, placed too low a value on stocks in the past.
But a lot happened in the 20th century to make stocks more attractive. The U.S. emerged as an economic superpower, and the economy became more predictable, especially as inflation and interest rates moderated.
With tools like mutual funds and 401(k)s, it's easier to buy stocks. And you've heard many times from your broker, the press, and books like Jeremy Siegel's "Stocks for the Long Run" that stocks have been consistent winners provided you hold them long enough.
Roughly half of Americans own stocks, up from 32 percent in 1989.
With high demand making stocks more expensive, it's reasonable to assume they have less room to rise; even the bullish Siegel expects after-inflation returns to be about a point lower than the long-run record.
Rob Arnott, a money manager and former editor of the Financial Analysts Journal, is even more pessimistic. "My message to boomers is simple," he says. "Don't count on the market to bail you out."
He's calling for a 6 percent long-run equity return (before inflation). Arnott has an elaborate set of calculations to back up this call, but you really needn't agonize over whether Arnott or Siegel has the right number.
What matters for your planning purposes is what could happen, and history shows that stocks can lose money, after inflation, for long periods. They declined at a rate of 0.4% from 1966 to 1981, Siegel notes. A bad stretch isn't such a problem when you're 30. But it can be a big problem after you've retired, especially if you were counting on 10 percent.
So don't count on it.