Secular bear market could last into 2010, maybe through 2020

Investors whose retirement nest eggs have taken a beating during the last two recessions shouldn't count on the markets bouncing back any time soon. As several experts have noted, there is mounting evidence that equity markets will be trending downward for a long time.

An emergent theory argues that the U.S. is in a "secular bear market," a long period in which equity markets experience flat or declining growth, punctuated by a series of bear market cycles. As the cycle progresses, each bear market cycle lasts longer and descends lower than the previous one, reaching lower and lower market bottoms and taking longer amounts of time to get there.