The depression had devastating effects in virtually every country, rich or poor. International trade plunged by half to two-thirds, as did personal income, tax revenue, prices and profits. Cities all around the world were hit hard, especially those dependent on heavy industry. Construction was virtually halted in many countries. Farming and rural areas suffered as crop prices fell by roughly 60 percent. Facing plummeting demand with few alternate sources of jobs, areas dependent on primary sector industries such as farming, mining and logging suffered the most.However, even shortly after the Wall Street Crash of 1929, optimism persisted; John D. Rockefeller said that "These are days when many are discouraged. In the 93 years of my life, depressions have come and gone. Prosperity has always returned and will again."

The Great Depression ended at different times in different countries; for subsequent history see Home front during World War II. The majority of countries set up relief programs, and most underwent some sort of political upheaval, pushing them to the left or right. In some states, the desperate citizens turned toward nationalist demagogues—the most infamous being Adolf Hitler—setting the stage for World War II in 1939.