<P> The 20th century British economist William Beveridge stated that an unemployment rate of 3% was full employment . 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 . </P> <P> 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 . </P> <P> What most neoclassical economists mean by "full" employment is a rate somewhat less than 100% employment . Others, such as the late James Tobin, have been accused of disagreeing, considering full employment as 0% unemployment . However, this was not Tobin's perspective in his later work . </P> <P> Some see John Maynard Keynes as attacking the existence of rates of unemployment substantially above 0%: </P>

When is an economy said to be at full employment