The number of U.S. residents without health insurance declined last year as employment-based coverage held steady, reversing a long downward trend, while coverage through government programs increased, the U.S. Census Bureau said Wednesday.

The number of uninsured in 2011 fell to 48.6 million, down from 50 million in 2010. The percentage without coverage fell to 15.7% a big drop from the 2010 uninsured rate of 16.3%, the Census Bureau said.

The number of people with health coverage increased to 260.2 million in 2011, up from 256.6 million in 2010.

The percentage of people covered through employer-sponsored plans in 2011 was 55.1%, which was not statistically different compared with the 55.3% coverage rate in 2010, the Census Bureau said.

By holding steady, 2011 marked the first time since 2000 that the coverage rate through employment-based plans did not fall, the Census Bureau said.

Similarly, the number of people in employer-sponsored plans inched up in 2011 to 170.1 million, which was not statistically different compared with 169.4 million in 2010.

The percentage of people covered through government programs increased.

For example, the percentage of the population covered by Medicaid — the federal-state program for the poor — rose in 2011 to 16.5%, up from 15.8% the previous year, and the number of people enrolled in Medicaid increased to 50.8 million from 48.5 million. The percentage of the population and the number of people enrolled in Medicaid are records.

The percentage and number of people enrolled in Medicare also set records last year. In 2011, 46.9 million people were enrolled in Medicare, up from 44.9 million, while the percentage of the population covered by Medicare increased to 15.2% from 14.6% in 2010.

At 3.4%, Massachusetts had the lowest uninsured rate of any state in 2011, according to the Census Bureau.

That is the result of a 2006 law that created a program in which the state subsidizes health insurance premiums of the low-income uninsured and imposes penalties on employers not offering coverage and assessments on individuals without health insurance coverage — except those who can prove that affordable coverage was not available and those who obtain special waivers.

Texas had the highest state uninsured rate at 23.8%.