Binyamin Appelbaum has a NYT blogpost suggesting that the economy may be growing more rapidly than the GDP imply based on the fact that national income has grown more rapidly in recent quarters. In principle, GDP, which measures the goods and services the economy produce, should be equal to national income, which measures the income generated in the production process. (Every cost to a buyer is income to someone.)

However, they never come out to be exactly equal. They measures of GDP and national income are done independently. The difference, the extent to which GDP exceeds output, is called the "statistical discrepancy."

Appelbaum's post points to a new paper that suggests that we should be taking an average of GDP growth and income growth as our actual measure of economic growth. If we go this route, then it implies that the recovery has been somewhat stronger (and the recession steeper) than the standard measure of GDP growth.

There is an alternative story. David Rosnick and I analyzed the movement of the statistical discrepancy and found a strong inverse correlation between the size of the statistical discrepancy and capital gains in the stock market and housing. This meant, for example, there was a large negative statistical discrepancy in 1999 and 2000 at the peak of the stock bubble (i.e. income exceeded output) which disappeared after the bubble burst.

The same thing happened in the peak years of the housing bubble, 2004-2007. In that case also, the large gap between the income side measure and the output side measure disappeared after the bubble burst.

The logic is simple. Some amount of capital gains will get misclassified in the national accounts as ordinary income. (Capital gains should not count as income for GDP purposes.) While this may always be true, when we have more capital gains, the amount of capital gains misclassified in this way will be greater.

This story fits the data pretty well. If our analysis is correct, then we are better off sticking with our old friend GDP as the best measure of economic growth.