In October 24th 1929, a record number of shares were traded on the New York stock exchange by panicking investors, marking the start of the market crash which lead to the Great Depression. Therein, companies borrowed more money to expand production to make more products, which backfired because now the demand for the product was so low companies weren't making money. Finally, when the depression hit, many companies had to make workers redundant to cut costs.
Because the banks were not able to give them money and when the banks went to depression then everyone wanted to get their money out of the bank and the bank didn't have th money to give so people were furious so Black Thursday and the Great Depression was bc if people had no money to buy stuff stores couldn't sell so they put it on sale
Reagan's time as President was so impactful on the USA that he is often quoted and his administration is often used as the gold standard when people are talking about national policy.