May Increase in Inventories Largest Since March

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Saturday, 10 July 2010 07:08

Yes, that would be another way of saying that the May increase was larger than the April rise, but that is what USA Today told readers. Actually inventories are a very important part of the recent pattern of growth in the economy.

During a recession inventories fluctuations tend to amplify swings substantially since it is the rate of change in the change of the stock of inventory (acceleration or deceleration) that affects GDP growth. During the downturn firms start to run down their inventories making a negative contribution to growth. When inventories stabilize, the fact that they are no longer declining adds to growth. Then when firms start to rebuild their inventories it adds even more to growth. Once firms have attained a normal rate of inventory accumulation, then inventories will provide little additional boost to growth even if firms continue to add to their inventories. 

This is very clear in the current recovery. The economy shrank at a -0.7 percent annual rate in the second quarter of 2009, it rose at a 2.2 percent rate in the third quarter, a 5.6 percent rate in the fourth quarter. The growth rate fell back to a 2.7 percent rate in the first quarter of this year. Nearly all of this variation was due to changes in the rate of inventory accumulation. There was little change in the pace of final demand growth over the last four quarters.

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The rate of inventory accumulation in the first quarter of 2010 was approaching its normal level. While inventory accumulation can be faster in any given quarter, it is unlikely to provide the sort of boost to growth that it did over the last three quarters. This means that GDP growth will be closer to the rate of final demand growth, which is looking pretty weak at the moment.