A look at the U-3 and U-6 Unemployment numbers.

This is a quick look at the U-3 unemployment rate vs the U-6 rate: 

CNBC: The Labor Department said Friday that the U-3 unemployment rate fell to 5.1 percent in August—but does that tell the real story? The BLS defines U-6 as "total unemployed, plus all persons marginally attached to the labor force, plus total employed part time for economic reasons, as a percent of the civilian labor force," plus all marginally attached workers. 

Note: The U-6 numbers are typically used against Democrats, while the U-3's lower rate is used exclusively to support Republican governors:
  

The U-6 rate dipped in August to 10.3 percent, the lowest since June 2008. The overall trend in the U-6 has been more volatile than the main unemployment rate (also known as the U-3). Take today's release (5.1) with a grain of salt, though: Jobs figures for the past ten Augusts have been revised upward by an average of 58,000 jobs, according to a Reuters analysis of news releases and subsequent revisions. August is the most common month for estimates to miss, likely due in part to seasonal adjustment.