The number of Americans who lacked health insurance for at least part of the year reached 52 million in 2010, report the Commonwealth Fund and Bloomberg News.
That number is roughly 40 percent higher than the 38 million who went without health insurance in 2001, according to the non-profit think tank's Biennial Health Insurance Survey.
The steep recession that began in December 2007 led to 9 million Americans losing their job-based health insurance coverage.
"This survey tells a story of millions of Americans who lost their jobs during the recession, lost their health benefits too, and had essentially no place to turn for affordable healthcare coverage--putting their health and financial security at risk," said Commonwealth Fund President Karen Davis.
Most of the uninsured were from low- and moderate-income households earning up to $44,100 per year. The average unweighted rate of uninsured was 47 percent, compared to a 13 percent rate of uninsured from higher-income households.
Davis noted that the Patient Protection and Affordable Care Act should guarantee that fewer individuals lose their healthcare coverage during another economic downturn.