During the Crash of 1929 proceeding theGreat Depression, margin requirements wereonly 10%. Brokerage firms, in other words,would loan $9 for every $1 an investor haddeposited. When the market fell, brokers calledin these loans, which could not be paid back.Banks began to fail as debtors defaulted ondebt and depositors attempted to withdrawtheir deposits en masse24, triggering multiplebank runs等