WASHINGTON -- The government's estimate of the number of Americans without health insurance fell by nearly 2 million yesterday, but not because anyone got health coverage.
The Census Bureau said it has been overstating the number of people without health insurance since 1995.
The bureau attributed the inflated numbers to a 12-year-old computer programming error.
The bureau reissued figures for 2005 and 2004 yesterday.
It plans to issue new numbers for every affected year in August, when the 2006 numbers are scheduled for release.
Health insurance statistics are widely cited in debates over the nation's system of healthcare, which is expected to be a big issue in the 2008 presidential election.
The revised estimates show that 44.8 million people, or 15.3 percent of the population, were without health insurance in 2005.
The original estimate was 46.6 million, or about 15.9 percent of the population.
"The total impact is small," said Ruth Cymber, the agency's director of communications.
She said similar reductions are expected in previous years, leaving historical trends unchanged.
In 2005, the percentage of people without health insurance was at its highest point since 1998, according to the original numbers.
Workers discovered the programming error when they were updating the computer system for the bureau's Current Population Survey, which yields data on income, employment, and health insurance coverage.
Some residents were counted as "not covered" by insurance when they had reported coverage.
No other questions in the survey were affected, Cymber said.
The error dates to the initial computerization of the monthly survey in 1995, she said.
"While it is certainly good news that fewer Americans are uninsured than previously reported, this raises major questions," said Representative Carolyn B. Maloney, Democrat of New York. "For an agency that specializes in statistics, 1.8 million is not a minor error; it's major error."
Maloney, who serves on the House subcommittee that oversees the Census Bureau, said the errors raise concerns about all census data.
Cymber said the bureau has improved its review standards and is updating its technology.
"We now have a formal process to make sure that we are using the latest technology," she said.