New Census Bureau health insurance figures suggest that the number of U.S. residents in employer-sponsored plans plunged 3.7% between 2008 and 2009.

The number fell of people in private employer-sponsored plans fell to a little below 170 million in 2009, according to census figures.

The group plan enrollment number fluctuated between 175 million and 180 million from 2000 to 2008, and, before that period, it had not been below 170 million since 1997, when the Census Bureau found about 166 million people in group health plans.

The share of the 304 million U.S. residents covered by private employer-sponsored plans fell to 55.8% in 2009, down from 58.5% the year before. The Census Bureau began recording detailed health insurance enrollment figures in 1987. In 2009, the share of the U.S. population in employer-sponsored plans dropped to the lowest level the bureau has recorded during that period.

The share started at 62.1% in 1987 and was above 60% in most years up until 2005. The bureau recorded a small drop between 2005 and 2006, and an accelerating rate of decline in subsequent years.

The only year when the percentage-point drop in employer plans’ share of the total market was as severe as it was between 2008 and 2009 came during the recession year of 1991, when the share dropped to

59.7%, from 60.4%

The total number of people with any kind of health coverage fell to about 254 million in 2009, from about 255 million, and the number of uninsured people increased to 51 million, from 46 million.

The drop in the overall number of people with coverage came as the number of people with Medicaid coverage climbed to 48 million, from 43 million.

Although uninsured rates were higher for lower-income households, the Census Bureau found the uninsured rate was still 9.1% for households with annual incomes of $75,000 or greater.

The drop in the number of people covered occurred before Congress passed the Affordable Care Act, the package that includes the Patient Protection and Affordable Care Act.

Karen Davis, president of the Commonwealth Fund, New York, says the new figures show how hard the recession has hit U.S. residents’ access to health care.

“Last year, nearly 7 million people lost coverage they previously obtained through an employer,” Davis says in a statement.

The figures show why middle-class families need the coverage subsidy options in the Affordable Care Act, the package that includes the Patient Protection and Affordable Care Act (PPACA), Davis says.

Health insurance groups have argued that the figures show the importance of eliminating government-imposed benefits mandates and making sure that any subsidies or other coverage access programs are designed to focus on providing aid to those most in need of help, to minimize distortion of the overall private health coverage market.