Wednesday, April 08, 2009

consequences of the oil shock of 2007-08

Econbrowser | In a paper presented at the Brookings Panel on Economic Activity Thursday, University of Calif.-San Diego economist James Hamilton crunched some numbers on how consumer spending responds to rising energy prices and came to a surprising result: Nearly all of last year’s economic downturn could be attributed to the oil price shock.

The paper uses a number of different models that had been fit to earlier historical episodes to see what they imply about the contribution that the oil shock of 2007-08 might have made to real GDP growth over the last year. The approaches surveyed include Edelstein and Kilian (2007), who examined the detailed response of various components of consumer spending, Blanchard and Gali (2007), who studied the extent to which the contribution of oil shocks has significantly decreased over time, a 2003 paper, which emphasized the role of nonlinearities, and a model-free data summary of the observed behavior of different economic magnitudes following this and previous oil shocks. Although the approaches are quite different, they all support a common conclusion: had there been no increase in oil prices between 2007:Q3 and 2008:Q2, the U.S. economy would not have been in a recession over the period 2007:Q4 through 2008:Q3.

One of the most interesting calculations was to look at the implications of the 2003 model. Using those historically estimated parameters to find the answer to the following conditional forecasting equation. Suppose you knew in 2007:Q3 what GDP had been doing up through that date and could know in advance what was about to happen to the price of oil. What path would you have then predicted the economy to follow for 2007:Q4 through 2008:Q4?

The answer is given in the diagram below. The green dotted line is the forecast if we ignored the information about oil prices, while the red dashed line is the forecast conditional on the huge run-up in oil prices that subsequently occurred. The black line is the actual observed path for real GDP. Somewhat astonishingly, that model would have predicted the course of GDP over 2008 pretty accurately and would attribute a substantial fraction of the significant drop in 2008:Q4 real GDP to the oil price increases.