The government statistic most commonly quotes is U3, which is the number of unemployed divided by total unemployed plus total employed. Unemployed is defined as people out of work who have actively looked for work within the last four weeks. Obviously that leaves a lot to be desired. There are other, more accurate statistics like U6 which considers unemployed and people who would like full time jobs but are working part time for economic reasons and those who have looked for work within the last year but not within the last four weeks. The U6 percentage is in the mid to upper teens.
Not really though, as the reporting of those looking for work is only tracked via unemployment insurance collection.
Thus, anyone looking for work that is not collecting unemployment would never be counted in this number. Thus, only people who lost a job and are still getting unemployment payments are counted. People entering the workforce for the first time, or who are not getting payments are not counted. As tracked by the government, this number will eventually reduce itself to zero, even if no one ever finds a job.
The fact that the official unemployment number has stayed so constant, actually means that real unemployment has been increasing steadily.