Inventories and the Wonders of GDP Accounting

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Wednesday, 22 December 2010 09:06

The news stories are coming out on the Commerce Department's release of revised data on 3rd quarter GDP and it seems that almost everyone has missed the story. The headlines of the articles are telling us that GDP growth was revised up slightly from 2.5 percent to 2.6 percent. While that may sound like at least somewhat positive news a more careful review of the data shows the opposite.

While the rate of GDP growth was revised up, the rate of final demand growth was revised down. Final demand, which is GDP excluding inventory accumulations, grew at just a 0.9 percent annual rate in the 3rd quarter, the same as its growth rate in the second quarter. The reason that GDP growth was revised upward was a more rapid reported growth in inventories.

The reported rate of inventory accumulation in the 3rd quarter was $121.4 billion (in 2005 dollars), the fastest pace ever. This added more than 1.6 percentage points to the rate of GDP growth in the quarter.

It is very unlikely that this pace of inventory growth will be sustained. Suppose that in the 4th quarter the rate of accumulation falls back to the pace of the second quarter. This would mean that inventories would subtract 1.6 percentage points from the growth rate. If final demand growth is 2.5 percent in the quarter (higher than it has been in any quarter of the recovery so far), then GDP growth would be just 0.9 percent.

In short, because the upward revision to GDP growth was based on more rapid accumulation of inventories it should not be viewed as a positive for the economy's growth prospects.