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 and minus the standard error of the estimate.