Wednesday, June 27, 2007

People Eat and They Drive

The Economist
knows the difference between the headline inflation and core consumer price index, and understands the importance of the former as an inflation indicator:

What the markets blithely ignored was the day's bad news. Headline consumer prices rose by 0.7%, the biggest monthly increase for nearly two years. Unlike core inflation, the headline measure includes fuel costs, which rose sharply, as well as food prices. For bond prices to rise on such a big jump in inflation, markets must be placing a great deal of faith in the core index as the true gauge of price pressures. Is that wise?

The cold-and-hungry index

The lure of core inflation as a barometer is that headline inflation rates tend to be volatile. Last June the annual headline rate in America, pushed up by soaring oil prices, was as high as 4.3%, but by October it had plunged to 1.3%. The rationale for excluding food and fuel is to filter out prices that jump around for temporary reasons, such as the vagaries of the weather or the messy politics of the Middle East. A good core index excludes this noise, leaving only the enduring part of inflation that reflects the weight of spending in the economy.

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