Answer:
Bought stocks on credit, thinking the value could only increase.
Step-by-step explanation:
Currently the securities and exchange commission (SEC) defines buying stocks on credit as buying through a margin account. This was a very common before the 1929 stock crash since investors speculated that the price of stocks would keep increasing. The notion that the stock prices could fall was not something considered possible back then. So when the market stooped growing, and the price of stocks started to lower, investors couldn't pay their loans and even if the securities were held as collateral, their value collapsed. Some people made huge fortunes doing this, but others lost everything.