The Great Depression was a severe worldwide economic contraction that began in 1929 and persisted through most of the 1930s, making it the longest and most broadly destructive economic downturn of the 20th century. It originated in the United States and spread rapidly to most of the industrialized world, producing mass unemployment, sharp deflation, steep declines in industrial output, widespread bank failures, and acute rural poverty. At its nadir in the United States, unemployment reached approximately 25 percent of the civilian labor force. The Depression had far-reaching political consequences, contributing to the rise of authoritarian movements in Europe, transforming the relationship between governments and their economies in the democratic world, and reshaping the international financial order. It ended at different times in different countries, with recovery in the United States generally dated to the late 1930s and early 1940s.

The Depression followed a decade of relative prosperity and speculative expansion in the United States known as the 1920s boom. The U.S. stock market crash of October 1929 — in which equity values fell catastrophically over several days, with the sharpest single-day losses on 28 and 29 October — is conventionally taken as the starting point, though economic historians debate whether the crash caused the Depression or was itself a symptom of underlying instability. A full account of the Depression's onset, progression, and uneven global impact is provided on the History page.

The contraction spread internationally through several channels: the contraction of American lending abroad, the collapse of commodity prices, the spread of protectionist trade policy (including the U.S. Smoot-Hawley Tariff of 1930), and the constraints imposed by the international gold standard. Countries that departed from the gold standard earlier generally recovered sooner. The human toll included not only unemployment but also hunger, internal migration, family dissolution, and a measurable decline in birth rates across affected nations.

The Great Depression is one of the most extensively studied events in economic history. Researchers have produced substantial empirical records of output, prices, employment, and financial conditions across dozens of countries. There is broad agreement on the broad factual chronology: the severity and duration of the contraction, its international scope, the role of banking panics in deepening the U.S. downturn, and the correlation between gold standard adherence and recovery timing.

Significant scholarly disagreement persists, however, on questions of causation, policy, and counterfactual history. The relative weight of monetary contraction, financial panic, fiscal policy, structural weaknesses, and international transmission mechanisms remains contested among economists and historians. The Depression also continues to generate debate in political economy about the proper role of government intervention in market downturns, the value of international monetary coordination, and the lessons applicable to later crises. See Great Depression — Debate.

Substantial expert consensus exists within economics on several specific questions related to the Depression — most notably on the role of monetary contraction and the Federal Reserve's failures in 1930–1933, a position associated especially with the research of Milton Friedman and Anna Schwartz and widely influential in subsequent scholarship. Consensus is considerably weaker on questions of fiscal policy effectiveness and on which policy interventions most explain cross-national variation in recovery timing. See Great Depression — Economics Consensus.

Monetarist Viewpoint Associated primarily with Milton Friedman and Anna Schwartz, this interpretation holds that the Federal Reserve's failure to prevent a collapse of the money supply transformed a serious recession into a catastrophic depression. On this view, the Depression was not an inherent failure of market capitalism but a policy failure by the central bank.

Keynesian Viewpoint Drawing on the framework developed by John Maynard Keynes, this interpretation emphasizes insufficient aggregate demand and argues that private investment and consumption cannot self-correct in a severe downturn without active fiscal stimulus. Government spending is seen as necessary to restore full employment.

Austrian Viewpoint The Austrian school, associated with Ludwig von Mises and Friedrich Hayek, attributes the Depression to credit expansion and malinvestment during the 1920s boom, which made a painful correction inevitable. On this view, government intervention and easy money prolonged rather than cured the downturn.

Institutionalist Viewpoint Some historians and heterodox economists emphasize structural factors — including wealth concentration, weaknesses in the banking system, agricultural distress predating 1929, and the institutional failures of unregulated financial markets — as preconditions that made the economy fragile before the crash.

International/Gold Standard Viewpoint A body of research, associated prominently with Barry Eichengreen and Peter Temin, locates the primary cause of the Depression's severity and international spread in the constraints of the interwar gold standard, which prevented monetary authorities from expanding credit and forced deflationary adjustments across countries.

New Deal Effectiveness Viewpoint Interpretations of the New Deal — the set of programs and reforms enacted under President Franklin D. Roosevelt beginning in 1933 — range from viewing it as a necessary and effective relief and recovery program to viewing it as having prolonged the Depression by introducing regulatory uncertainty and labor market rigidities.

• Great Depression — History
• Great Depression — Debate
• Great Depression — Economics Consensus
• Monetarist Viewpoint
• Keynesian Viewpoint
• Austrian Viewpoint
• Institutionalist Viewpoint
• International/Gold Standard Viewpoint
• New Deal Effectiveness Viewpoint
• New Deal
• Federal Reserve
• Gold Standard
• Great Recession
• Smoot-Hawley Tariff

<references/>

1. Milton Friedman and Anna Jacobson Schwartz, A Monetary History of the United States, 1867–1960 (Princeton University Press, 1963), chapters 7–8.
2. Barry Eichengreen, Golden Fetters: The Gold Standard and the Great Depression, 1919–1939 (Oxford University Press, 1992).
3. Peter Temin, Lessons from the Great Depression (MIT Press, 1989).
4. Christina D. Romer, “The Nation in Depression,” Journal of Economic Perspectives 7, no. 2 (1993): 19–39.
5. Robert A. Margo, “Employment and Unemployment in the 1930s,” Journal of Economic Perspectives 7, no. 2 (1993): 41–59.
6. Gene Smiley, Rethinking the Great Depression (Ivan R. Dee, 2002).
7. Harold L. Cole and Lee E. Ohanian, “New Deal Policies and the Persistence of the Great Depression: A General Equilibrium Analysis,” Journal of Political Economy 112, no. 4 (2004): 779–816.
8. Charles P. Kindleberger, The World in Depression, 1929–1939, revised ed. (University of California Press, 1986).