What caused the population trend known as the Great Migration? Slavery was abolished, and former slaves wanted to leave the South. Slavery was abolished, and former slaves wanted to leave the South. Economic troubles made sharecropping difficult, and industrial jobs were created in the North. Economic troubles made sharecropping difficult, and industrial jobs were created in the North. Wars and economic problems in Europe led to a vast increase in immigration. Wars and economic problems in Europe led to a vast increase in immigration. Growing concerns about yellow fever in the South spurred many individuals to look westward. Growing concerns about yellow fever in the South spurred many individuals to look westward.