Enrollment in health savings accounts linked to high-deductible health insurance plans grew last year among large U.S. employers at nearly three times the rate among small employers, a survey shows.

In fact, the fastest growing market for HSA/HDHP products is large-group coverage, which has grown from 19% of the market in March 2005 to almost 50% of the market as of January, according to the survey conducted by the Washington-based trade association America's Health Insurance Plans.

The survey, which was released last week, found that more than 2 million employees of large companies were enrolled in HSAs in January of this year, up from 679,000 a year earlier and just 162,000 in March 2005, the first year that HSAs were widely available.

Although enrollment was a bit slower in the small-group and individual markets, it also surged. Enrollment in small-group HSA plans more than doubled to 1.1 million in January from 510,000 a year earlier. By comparison, individual market plans gained 29%, with enrollment totaling 1.1 million in January compared with 855,000 in January 2006.

Approximately 4.5 million people were covered by HSA/HDHP products, according to the AHIP census, a 43% increase since last year.

Going mainstream

"When you have in the large-group market a tripling in a year," it shows that HSA plans "are quickly becoming a mainstream option," said Michael Tuffin, a senior vp at AHIP.

He said the growth rate is phenomenal given that the product is little more than two years old. While HSAs were authorized by Congress under a 2003 law and have been available since Jan. 1, 2004, many employers waited to offer the plans until the Treasury Department issued guidance in August 2004 that resolved many operational concerns that had been raised about HSAs.

"The first real shot that employers had to offer this was 2005, and here we are January of '07 with these numbers. That's not insignificant," Mr. Tuffin said.

He said the findings should assure other employers that are thinking about adding HSAs to their health plan options.

"Employers large and small are incorporating health savings account plans into their offerings for employees," he said.

While the growth rate for large employers and small-group employers was exceptional, the tempering of enrollment gains experienced by the individual market slowed the overall growth rate for Jan- uary to less than half that seen between March 2005 and January 2006.

Mr. Tuffin attributed this slowdown to the "natural maturing of a marketplace."

"I think 43% growth by any definition is robust and indicative of success. Nothing's going to grow at 200% forever," he said.

Moreover, "in a market that has a very low growth rate as a whole, to have one aspect of that market grow by 43% in a year shows that something's happening," Mr. Tuffin said.

The full report is available at www.ahipresearch.org.