The post–World War I recession was an economic recession that hit much of the world in the aftermath of World War I. In many nations, especially in North America, economic growth continued and even accelerated during World War I as nations mobilized their economies to fight the war in Europe. After the war ended, the global economy began to decline. In the United States, 1918–1919 saw a modest economic retreat, but the second part of 1919 saw a mild recovery. A more severe recession hit the United States in 1920 and 1921, when the global economy fell very sharply. August 1918 – March 1919 · 7 months Business activity: −24.5% Severe hyperinflation in Europe took place over production in North America. This was a brief but very sharp recession and was caused by the end of wartime production, along with an influx of labor from returning troops. This, in turn, caused high unemployment. Dates: the National Bureau of Economic Research's business cycle chronology. Wiki link Wiki link