The widely followed monthly gauge of U.S. unemployment and payroll jobs normally comes out on the first Friday of each month, but not this time. As to why, well, it's definitely TMI for most of us, but CNBC does offer an explanation:
The Labor Department's Bureau of Labor Statistics issues the report on the third Friday following the conclusion of the so-called "reference week", in which the household surveys are conducted. The "reference week" is the week that includes the 12th of each month, which usually puts the report's release date on the first Friday of the following month. However, due to the vagaries of the calendar, that's not always the case. This time around, the 12th occurred on a Sunday, pushing the "reference" Friday to February 17, and the release date to March 9.
See what I mean? Actually, the delay to next Friday is a reminder of how tentative these numbers can be. Felix Salmon tried to explain last year:
Essentially, the U.S. Department of Labor sends out forms asking employers to report on their payrolls every month. The companies report what their payroll figures are for whichever pay period included the 12th of the month. The Bureau of Labor Statistics then collates all that data, and three Fridays after the 12th of the month, it releases a preliminary estimate for how many people had jobs that month, how much they were paid, and so on.
The point here is that the payrolls report is a snapshot of a point in time; it's not something you get from adding up daily data from each of the days in the month. And the snapshot is taken on the 12th of the month, not at the end of the month. The markets love the payrolls report because it's super-fast, rather than because it's super-accurate: it's the closest thing we have to an official national data series showing how the economy's doing right now.
This helps explain why the revisions from previous months can be so substantial.