Unemployment occurs when a person is available to work and seeking work but currently without work. The prevalence of unemployment is usually measured using the unemployment rate, which is defined as the percentage of those in the labor force who are unemployed. The unemployment rate is also used in economic studies and economic indices such as the United States' Conference Board's Index of Leading Indicators as a measure of the state of the macroeconomics.

Most economic schools of thought agree that the cause of involuntary unemployment is that wages are above the market clearing rate. However, there are disagreements as to why this would be the case: the economists argue that in a downturn, wages stay high because they are naturally 'sticky', whilst others argue that minimum wages and union activity keep them high. Keynesian economics emphasizes unemployment resulting from insufficient effective demand for goods and services in the economy (cyclical unemployment). Others point to structural problems, inefficiencies, inherent in labour markets (structural unemployment). Classical or neoclassical economics tends to reject these explanations, and focuses more on rigidities imposed on the labor market from the outside, such as minimum wage laws, taxes, and other regulations that may discourage the hiring of workers (classical unemployment). Yet others see unemployment as largely due to voluntary choices by the unemployed (frictional unemployment). Alternatively, some blame unemployment on Globalisation. There is also disagreement on how exactly to measure unemployment. Different countries experience different levels of unemployment; traditionally, the USA experiences lower unemployment levels than countries in the European Union, although there is variant there, with countries like the UK and Denmark outperforming Italy and France and it also changes over time (e.g. the Great depression) throughout economic cycles.