There is a pleasant surprise in the latest batch of economic data released Thursday by the Bureau of Economic Analysis. Buried deep inside the government’s revised estimate of fourth-quarter growth (revised but unchanged at 3 percent annualized) is an alternate measure of economic activity that is winning increased attention. And by that alternate measure, gross domestic income, the annualized pace of growth in the final three months of 2011 actually climbed to 4.4 percent.

That’s the kind of growth we usually see during an economic recovery, the kind of growth that’s fast enough to create new jobs. Indeed, it suggests that we may have learned the answer to a fretful mystery. Until now, economists have struggled to explain why unemployment was falling so fast when the major measure of growth, gross domestic product, was rising at an exceedingly modest pace.

The Federal Reserve chairman, Ben S. Bernanke, said Monday that in his view the most likely explanation was that the pace of job growth was not sustainable.

The data released Thursday suggests an alternative explanation: the government’s estimate of gross domestic product may be understating the actual pace of growth. The estimate of gross domestic income may be closer to the truth.

Source: Bureau of Economic Analysis

As I wrote in an article last year, the two measures should produce identical results. Gross domestic product emphasizes spending; gross domestic income measures … income. And “a penny spent is a penny earned by someone else. But estimates of the two measures can diverge widely, particularly in the short term, and a body of recent research suggests that the income estimates are more accurate.”

A growing number of economists argue that the government should incorporate both methods to improve the quality of its primary estimate of economic activity. A 2011 paper provides a good account of the case for doing so.