Aggregate Hours
  
The government produces a lot of data about the economy. These regurgitations include calculations about the labor market as a key indicator of where the economic winds are blowing. The most common figures quoted by the news media include things like jobs numbers (and not the kind commonly found on Craigslist), meaning the number of jobs added in a given period, and unemployment rate.
However, this isn't the most accurate number to determine the amount of work being done in the economy. Reporting the number of people who are working disguises the fact that not everybody works the same amount. Some people are part-time, some people are full-time...and even within those groups there is variation on the number of hours being worked. And there are contractors. Think: Uber and Lyft drivers, who skew those total labor stats.
Reporting aggregate hours helps clear up this confusion. The figure represents the total of all hours being worked. The government reports it for the country as a whole and for individual industries. It gives a clear idea of the labor input needed to produce the stuff we are producing.