The unemployment number has been measured the same way for a long time. It has also been used by people running for office for a long time. Just because it does not currently support your objective does not make it invalid.
http://www.bls.gov/cps/cps_htgm.pdf
"Is there only one official definition of unemployment?
Yes, there is only one official definition of unemployment, and that was discussed above. However, some have argued that this measure is too restricted, and that it does not adequately capture the breadth of labor market problems. For this reason, economists at BLS developed a set of alternative measures of labor underutilization. These measures are published every month in the Employment Situation news release. They range from a very limited measure that includes only those who have been unemployed (as officially defined) for 15 weeks or more to a very broad one that includes total unemployed (as officially defined), all persons marginally attached to the labor force, and all individuals employed part time for economic reasons."