Full employment, in macroeconomics, is the level of employment rates where there is no cyclical or deficient-demand unemployment. It is defined by the majority of mainstream economists as being an acceptable level of unemployment somewhere above 0%. The discrepancy from 0% arises due to non-cyclical types of unemployment, such as frictional unemployment (there will always be people who have quit or have lost a seasonal job and are in the process of getting a new job) and structural unemployment (mismatch between worker skills and job requirements). Unemployment above 0% is seen as necessary to control inflation in capitalist economies, to keep inflation from accelerating, i.e., from rising from year to year. This view is based on a theory centering on the concept of the Non-Accelerating Inflation Rate of Unemployment (NAIRU); in the current era, the majority of mainstream economists mean NAIRU when speaking of ""full"" employment. The NAIRU has also been described by Milton Friedman, among others, as the ""natural"" rate of unemployment. Having many names, it has also been called the structural unemployment rate.The 20th century British economist William Beveridge stated that an unemployment rate of 3% was full employment. Other economists have provided estimates between 2% and 13%, depending on the country, time period, and their political biases. For the United States, economist William T. Dickens found that full-employment unemployment rate varied a lot over time but equaled about 5.5 percent of the civilian labor force during the 2000s. Recently, economists have emphasized the idea that full employment represents a ""range"" of possible unemployment rates. For example, in 1999, in the United States, the Organisation for Economic Co-operation and Development (OECD) gives an estimate of the ""full-employment unemployment rate"" of 4 to 6.4%. This is the estimated unemployment rate at full employment, plus & minus the standard error of the estimate.The concept of full employment of labor corresponds to the concept of potential output or potential real GDP and the long run aggregate supply (LRAS) curve. In neoclassical macroeconomics, the highest sustainable level of aggregate real GDP or ""potential"" is seen as corresponding to a vertical LRAS curve: any increase in the demand for real GDP can only lead to rising prices in the long run, while any increase in output is temporary.