The public small-business exchanges, however, are the only way employers can now avail themselves of the tax credits available, and a recent analysis of the plans by Mr. Gabel of NORC showed them to be less expensive, on average, than the ones available outside of the exchanges.

And some employers say they have clearly benefited. Robert S. Jaffe, president of Consensus Systems Technologies, in Shenorock, N.Y., was able to save about $32,000 by going through the exchanges to buy coverage for six employees. He chose Health Republic Insurance, a new co-op plan created under the law, for people who lived in the area. While he was initially concerned about the insurer, he says he was reassured by the care it gave a worker needing a liver transplant.

But some employers have been unimpressed with the options available through the marketplaces. "What I see on the exchange is junk," said Bill Frerichs, the owner of Frerichs Freight Lines in Belleville, Ill., a trucking business. He opted to stay with the coverage he had from Coventry Health Care, owned by Aetna.

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But even some of those who have taken advantage of the law to continue providing coverage say they worry about the future. Annie Grove, who along with her husband, Matt, owns Bagel Grove in Utica, N.Y., has about 20 employees, some of whom are covered under Medicaid. She offers a high-deductible plan to six of them, including herself, and uses the tax credit to help pay for about half of the cost. Ms. Grove says she is still unsure how long she will be able to pay for coverage, especially when the tax credits expire after two years and she can no longer use the money for premiums.

"My biggest concern is when the tax credits go away," she said.

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No health insurance for small business