Saturday, March 28, 2009

Revisions to Government-Issued Data

from John Mauldin:
Typically with these government statistics, you get a preliminary number, which is a guess based on past trends, and then as time goes along that data is revised. In recessions like we are in now the revisions are almost always negative.

There is no conspiracy here. The people who work in the government offices have to create a model to make estimates. Each data series, whether new home sales, employment, or durable goods sales, etc., has its own unique sets of characteristics. The estimates are based on past historical performance. There is really no other way to do it.

So, past performance in a recession suggests higher estimates than what really happens. Then, the numbers in the following months are revised downward as actual numbers are obtained. But the estimates in the current months are still too high. That makes the comparisons generally favorable, at least for one month. And the media and the bulls leap all over the "data," and some silly economist goes on TV or in the press and says something like, "This is a sign that things are stabilizing." It drives me nuts.

Ignore month-to-month estimated data. The key thing to look for is the direction of the revisions. If they are down, as they have been for over a year, then that is a bad sign. Further, one month's estimates are just noise. Look at the year-over-year numbers. When the direction of the revisions is positive and the year-over-year numbers are starting to stabilize, then we will know things are starting to turn around.