The Great Depression was the worst economic slump ever in U.S. history, and one that spread to the entire industrialized world. Banks, stores, and factories were closed and left millions of Americans jobless, homeless, and penniless. Many people came to depend on the government or charity to provide them with food. This led to a hard decrease in world trade as each country tried to protect their own industries and products by raising fees on imported goods. The economy continued to fall almost every month. The period was the longest and worst period of high unemployment and low business activity in modern times.