The difference

There is one right lesson (among the many wrong lessons) that authorities learnt from the Great Depression:
keep international trade intact:
Read this from The Economist:
"DURING the Great Depression, America’s protectionist Smoot-Hawley Act of 1930 raised tariffs on more than 900 goods. A series of retaliatory actions by other countries followed. The effect on global commerce was devastating. In the three years to June 1932, the volume of world trade shrank by over a quarter. No wonder, then, that the spectre of the worst recession since the Depression led many to fear another descent into protectionism and a similar decline in trade.
At first, the recession did hit trade hard. Global GDP fell by 0.6% in 2009 while the volume of world exports dropped by 12.2%. But whereas the Depression saw trade decline for at least four years, this time the rebound has been quick, and sharp. By May this year, emerging-economy members of the G20 were importing and exporting around 10% more than their pre-crisis peaks (see chart). Rich-world trade has recovered from the trough too, though it has not yet made up all the ground lost since the credit crunch began..."
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Comment: Forget about stimuli which only have made things worse. Praise our leaders that at least one thing they did not dare to mess up: international trade. Yet we're not yet safe: because governments in a completely UNNECESSARY way added one stimulus program upon the next, they are now fully in debt and may --- God forbid -- resort to protection. Note the irony: At first international trade saved us. Yet authorities learnt this right lesson along with many false lessons. The false lessons that they have learnt may lead them to negate the only right lessons they had learnt so far.