The Great Depression, was worldwide crisis that spanned 1928 to 1933, caused wide-spread unemployment, bankruptcy, business failure, and price inflation. This tragedy left millions of previously-employed Americans without jobs and in poverty. And in Germany, the 20-million-strong workforce dropped to 11 million.
One of the main causes of the Great Depression, if not its main cause, was its timing: the cost of World War I left many countries--especially Germany--in debt, which led them into spiraling despair. This also made it difficult to reintroduce the gold standard on which the world previously relied. Consequently, it became a challenge to have a working trading system.
Another related economic factor that spurred the Great Depression was the fall of America's trade markets. Trading markets at home and worldwide faced difficulty and many even dissolved.
Increased tension between global superpowers following World War I also caused many trade agreements to collapse. In turn, this spurred overproduction, which then led to dropped prices for goods. Ultimately, because of this, many businesses were unable to pay their employees well, thus resulting in a terrible cycle of unemployment and poverty.
Due to these horrific economic conditions, several democratic countries resorted to autocracy, or dictatorship. Britain, however, was one of the few countries less effected by the Great Depression; because of its large markets, democracy survived here.
The Great Depression's effect on many countries was lasting and devastating. Undoubtedly one of the worst economic downfalls in world history, the Great Depression led the then newly-elected American President Roosevelt was able to create one of the most famous initiatives in American history-development, as it created jobs for unemployed Americans and overall made a large difference in decreasing the effects of the Great Depression.
[Source: The Complete History of the World]