At the end of the 1920's most of the world's markets spiraled in to the ground in one gigantic FeedbackEffect. The funny thing about this was that no material wealth disappeared. It's just that one day people agreed they were rich, and the next they agreed they were poor.

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There were however flows of material wealth between entities (individuals and / or companies) that made some people poor (in the extreme bankrupt) who had previously been richer.  PaulRedman

''And, you imply, enriched others. Were there really people who profited by the GreatDepression? Looking at it as a human struggle, it seems the people who won out were the reformers and the warriors. And eventually the arms-merchants. Were there others?''

The ones who kept their heads and could afford to buy when everyone else was selling, i.e. those rich enough (or perhaps diversified enough) not to be materially affected.

''Anyone in particular? Got any names?''

Marshall Field's built Chicago's Merchandise Mart -- the largest building in the world until the Pentagon was built -- to consolidate their wholesale activities under one roof.  The Mart was completed 6 months into the Depression but Field's was hit so hard they eventually liquidated their wholesale division.  Joseph P. Kennedy, the Kennedy family patriarch and father of JFK, bought the Mart from Field's for $12.5 million, less than half the construction costs.  Until very recently, it had been the greatest source of income for the family.  The Kennedy family sold the Mart (along with some other properties) in 1998 for $625 million.

''Many government employees went through the Depression without great hardship.  They kept their jobs and salaries, and prices of goods and services went down, so their standard of living rose.''

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Actually, the problem was that the flows slowed due to uncertainties about the future.  Total material wealth is not as important to the health of an economy as is the willingness of people to trade what they have for what they want, and the willingness to trade for things today that will have greater value in the future.