According to the U.S. Department of Labor, Bureau of Labor Statistics, "unemployed persons (Current Population Survey) [are] persons aged 16 years and older who had no employment during the reference week, were available for work, except for temporary illness, and had made specific efforts to find employment sometime during the 4-week period ending with the reference week. Persons who were waiting to be recalled to a job from which they had been laid off need not have been looking for work to be classified as unemployed. Unemployment rate…represents the number unemployed as a percent of the labor force."
U.S. Department of Labor, Bureau of Labor Statistics (BLS). Local Area Unemployment Statistics, Annual Average, “Unemployment rates for states, [Year]” and “Labor force data by county, [Year] annual averages”.
Available at: http://www.bls.gov/lau/home.htm
Updated May 2018.
Includes revised figures for 2010-2016.