Lost Decades

"How concerned should investors be about the possibility of have a 10-year stretch with negative equity returns? RPSeawright addresses this all-important question for retirees or near-retirees:

A Journal of Financial Perspectivespaper from last summer considers how unusual it really is for equity markets actually to “lose a decade.” As it turns out, lost decades of this sort are not the exceptional episodes that only very rarely interrupt normal steady economic growth and progress that so many seem to think.
In the paper, Brandeis economist Blake LeBaron finds that the likelihood of a lost decade — as assessed by the historical data for U.S. markets via a diversified portfolio — is actually around 7 percent (in other words, about 1 in 14). Adjusting for inflation (using real rather than nominal return data) makes the probability significantly higher (more like 12 percent, nearly 1 in 8). The chart below (from the paper) shows the calculated return (nominal in yellow, real in dashed) for ten-year periods over the past 200+ years, and shows six periods in which the real return dips into negative numbers.

So a “lost decade” actually happens fairly frequently. As LeBaron summarizes:

The simple message here is that stock markets are volatile. Even in the long-run volatility is still important. These results emphasize that 10-year periods where an equity portfolio loses value in either real or nominal terms should be an event on which investors put some weight when making their investment decisions..."

at  http://systematicrelativestrength.com/2014/04/24/lost-decades/