Howard Pyle, The Burning of Jamestown, an early-twentieth-century illustration, not an eyewitness view. Public domain.
In the last week of October 1929, stock prices broke, margin calls went out, and brokers sold the shares of customers who could not pay.
A household that owned no shares lost no brokerage account that week, and its exposure was a job or a bank that had been living off the boom.
A household that had bought shares on margin with savings could be sold out in a day, and the account could close below what the family had put in.
A buyer who held shares with cash and no debt against them could wait, and a broker who could still borrow could keep the doors open, so the same week did not treat every owner alike.
Each forced sale lowered the price that triggered the next call, so the selling fed on itself.
The week destroyed a great deal of paper wealth and a great many small margin accounts.
It did not, by itself, empty the country’s bank accounts or its payrolls, and the harder damage was the break in credit, farms, and jobs that this collapse set in motion.
Galbraith, The Great Crash, 1929 (1955)