The causes of the Great Depression are still a matter of active ebate among economists. The specific economic events that took place during the Great Depression have been studied thoroughly: a deflation in asset and commodity prices, dramatic drops in demand and credit, and disruption of trade, ultimately resulting in widespread poverty and unemployment. However, historians lack consensus in describing the causal relationship between various events and the role of government economic policy in causing or ameliorating the Depression. One popular theory is that the Depression was caused by the vast economic boom in the 1920's, and that by the time the boom reached its peak in 1929, investors became fearful of their stock shares as markets expanded some focus to Europe, which still had nations that were economically damaged from World War I.