Extrait du WSJ

« A big upward revision to gross domestic product, now seen increasing at a 3.7% pace in the second quarter, has reassured some economists that the economy is on solid footing heading into the second half of the year.

But a less closely watched number in the Commerce Department report provides a fair amount of caution.

An alternative measure of economic output, gross domestic income, advanced at a much slower 0.6% pace last quarter. By that gauge, economic growth barely inched ahead in the first half of the year. (GDI advanced at 0.4% pace in the first quarter versus a 0.6% increase for GDP.)

GDI and GDP measure the same thing: the size of the economy. GDP measures production based on what is spent by consumers, businesses and governments, while GDI measures the income generated from production. So, things like wages, corporate profits and taxes.

In theory, the two measures of output should be identical. But since they come from different source data, they can differ widely from quarter to quarter. For example, in the first quarter of 2012, GDI advanced 7.7%, while GDP increased at a 2.7% pace. In the third quarter of 2007, GDI fell at a 2.2% pace but GDP advanced 2.7%. Both measures are adjusted for inflation.

Some economists suggest putting greater weight on the GDI measure.

Federal Reserve economist Jeremy Nalewaik, in a 2006 paper, argued that GDI is a better predictor of recessions than GDP.

The president’s Council of Economic Advisers advocates for considering a blend of two measures. A report published last month noted an average of GDI and GDP “is a better predictor of future revisions to the data” than considering the initial read of GDP alone.

That could indicate Thursday’s GDP figure could be downgraded when government number crunchers incorporate more comprehensive data.

The Commerce Department acknowledged those views, to a degree, in Thursday’s report by publishing the average of GDI and GDP for the first time. It showed 2.1% growth last quarter.

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