The “Depression of 1921” has been receiving a lot of attention recently (Krugman, Selgin, Murphy, and Sumner) mostly in response to James Grant’s The Forgotten Depression:1921: The Crash That Cured Itself. The argument of the book is that the economy recovered more quickly because neither the federal government nor the Federal Reserve attempted to pursue activist policies. I am skeptical that 1921 is a useful case to generalize from.
It was a post war recession, much like the one after World War II. Most business cycle movements have been associated with busts after periods of credit expansion (see the recent work of Alan Taylor et al). In those cases it was households and businesses that borrowed and spent during the boom. Consequently, when the bust comes, businesses and consumers struggle to repay their debts. Businesses fail and consumers default. Even consumers who do not go bankrupt reduce their current spending to avoid default (see Martha Olney). As businesses and households default the value of bank assets fall and banks fail. The bank failures result in decreases in the money supply (Friedman and Schwartz) and disintermediation (Bernanke). In other words, it creates a real mess when people take on excessive amounts of debt, especially when they use that debt to bid up the prices of assets like stocks or real estate.
In terms of increases in output and prices, war time booms look similar to credit fueled booms, but the government is the one borrowing and spending. The end of the boom does not necessarily lead to a financial crisis or reductions in consumption and investment. Granted government borrowing can also create a mess, particulalry if people begin to doubt its willingness or ability to pay, but that hasn't really been an issue for the U.S.
I also have a problem with calling this a depression. I know that there is no universally accepted definition of the term depression. And I know that Grant is not the first to refer to this episode as a depression. But we completely lose any distinction between a recession and a depression if this was a depression. Neither the length nor the severity of the decline in real GDP warrant the term depression.