Recently, a number of financial pundits have been predicting that stock market returns will be "substantially below average" in the coming decades.

Sometimes the statement is made that way, other times it is cloaked in financial speak making reference to a decrease in "the equity risk premium."

They could be right.  Stock returns and everything associated with them (corporate earnings, P/E ratios, etc) are incredibly unpredictable.

But what is prompting this feeling among the fortune-tellers?  It could be a heaping helping of recency bias (believing the future will be similar to the very recent past).

According to Jeremy Siegel's research, dating back to 1871, there have been 14 ten-year periods of negative real (after-inflation) returns for stocks (including the one just ended).

In the decade following every previous "lost decade," inflation-adjusted stock returns exceeded 10%.