“Is the economy pulling itself out of a slump, or is it sinking deeper?” asks Daniel Altman in today’s New York Times.

“The answer could be either, based on the data from government agencies these days. Because they measure the same things — employment, incomes and prices — in different ways, it can be hard to tell what is really happening.”

“Yet among all the alternative gauges, some of the most widely cited data is collected in a patchwork fashion, or checked against benchmarks only once a decade. What is more, frequent changes in the agencies’ methods can make comparisons with earlier trends impossible. And a few economists complain that those revisions may be motivated by politics rather than science.”

” ‘This is not a customer-driven enterprise,’ said Daniel J. B. Mitchell, a professor of management and public policy at the University of California at Los Angeles. ‘It’s not always clear to me that we’re getting the services that we’d hope for.’ “

“Many Americans have been watching data from the job market, but those figures can sometimes be misleading. The Bureau of Labor Statistics reported last week that payrolls outside farming had dropped by 30,000 in June, on a seasonally adjusted basis. In the same report, it said that the total number of employed people had grown by 251,000.”

“Was the labor market stagnating, or booming?”

“Neither number represented an absolute truth. The figure for payrolls comes from reports by businesses and government that are checked once a year against unemployment insurance records, which are fairly comprehensive. But the figure for employed people comes from a sampling of households that is thoroughly benchmarked only once a decade, with the census.”

” ‘Particularly if you are interested in employment as a measure of economic trends, you probably want to use the payroll survey more than the household survey,’ Professor Mitchell said. ‘Things that are proportions, percentages, ratios — that’s what I would say you want to use the household survey for.’ “

“Thomas J. Nardone, who supervises the survey of households as chief of the bureau’s division of labor force statistics, said Professor Mitchell’s approach was basically correct for short periods. ‘You have to be careful about interpreting things, especially if you’re dealing with just one additional bit of information.’ “