The economy had been growing fluidly for the Roaring Twenties. But the first sign of trouble was on Black Thursday. At that time, the stock exchange was around 4 million shares each trading day. But on Black Thursday, a record 12.9 million shares were exchanged. The systems for tracking the market prices could not keep up with trading volume, and that may have contributed to panic selling on that day. Panic selling brought the market to the ground. The simple laws of supply and demand were in place. With no one left willing to buy stocks, and everyone trying to sell at the same time, the market had nowhere to go but down. The significance if the Stock Market Crash because it marked the start of the Great Depression, the largest economic downturn in American history, causing millions to become jobless and thousands to lose their life savings. People began going starving and living in bad conditions, until a series of government decisions believe it or not, gave jobs to people, and so did WWII.