All major depressions are caused by

Sudden and breathtaking technological breakthroughs which make many past bets go bad.

Productivity and Depressions

The Nordhaus study of productivity and employment:

Based on a range of measures, U.S. productivity growth has averaged 2 to 3 percent per year in the period 1995-2004, compared with less than 1.5 percent per year from 1973 to 1995. The strong productivity growth of the past decade is comparable with the 1948-73 period. The two peak years in the recent period have equalled the peaks of the earlier 1948-73 period. The improvement in productivity growth has survived the stock market bust of 2000, the subsequent decline in investment, a recession, rising fiscal deficits, wars, and skyrocketing oil prices.

Just prior to the crash we suffered productivity gains comparable to the most productive period in history? Isn't this the same result from the Great Depression?