Unlike most economic data from the U.S. government, the monthly unemployment rate isn't usually revised later. If, for example, the Labor Department says the rate was 7.7 percent in a particular month, that rate normally stays 7.7 percent.
Until January, that is.
Every January, the government updates the formulas it uses to calculate unemployment data. The new formulas can change some of the rates for the previous five years. Typically, though, only a few of the monthly rates are revised.
On Friday, the government revised the unemployment rates for two months in 2012. The rate for November, first reported Dec. 7, was revised up to 7.8 percent from 7.7 percent. And the rate for July was revised down to 8.2 percent from 8.3 percent.
By contrast, monthly job creation numbers are revised twice in the two months after they're first released. They're also revised annually. The result is a frequently substantial gap between an initially reported jobs total and the final revised total.
For example, the government initially said employers added only 96,000 jobs in August. That wouldn't generally be enough to lower the unemployment rate. But the number jumped after two revisions to a robust 192,000.
The unemployment rate for that month still stands at 8.1 percent — just as the government originally reported.