There are a few ways to measure unemployment, but it is normally interpreted as a percentage of the working-age population that does not have a job.

The statistics that are used to determine unemployment rate typically use the number of unemployed people who are actively searching for a job. The Bureau of Labor Statistics conducts a monthly poll called the Current Population Survey which goes out to about 50,000 households, and this is a significant source of unemployment data.

Milton Friedman won a Nobel Prize partially for his theory that there is a Natural Rate of Unemployment, which is normal and can be determined using certain current data. According to that theory, we should only be concerned with unemployment when it rises so far above the natural rate.

Critics of the unemployment rate in general argue that the statistics only account for the number of people who are still actively looking for work, and disregards the real number of unemployed working-age people, since many of them may not be looking for work anymore.