“The companies realized they cannot continue to be a social insurance system for the American people,” he said by e- mail. Businesses, he said, have been “woken up by the ACA.”

Aon Jumps

Aon jumped 5.6 percent in New York trading yesterday, after the Walgreen announcement. Insurers fell. Investors are worried their business may suffer in the transition away from traditional benefits, Matthew Borsch, a Goldman Sachs Group Inc. analyst, said in a note to clients.

The slide continued today. UnitedHealth Group Inc., the biggest U.S. health insurer, fell 1.8 percent to $71.70 at 11:46 a.m. New York time. Cigna Corp. dropped 2 percent.

Employers that announced changes in recent weeks said the health-care overhaul was one consideration among many. The law will raise costs for some businesses by imposing new taxes and requiring more generous benefits for existing workers.

UPS Benefits

United Parcel Service Inc. said in August it would no longer provide benefits to employed spouses of 15,000 non-union workers, since they must be offered coverage by their own companies under the Affordable Care Act. Atlanta-based UPS also cited rising medical costs in general for their decision, particularly expenses for chronic conditions such as diabetes and heart disease.

International Business Machines Corp. and Time Warner Inc. followed with word they would send retirees to the private exchanges, with company stipends to help pay for coverage.

IBM, based in Armonk, New York, said the move was made to help keep premiums low for the 110,000 Medicare-age workers affected by the switch.

Last week, Trader Joe’s Co., the closely held supermarket chain, said it would end health benefits next year for part-time workers. Employees will get a $500 payment next year and be sent to the public exchanges. With the federal tax credits available there, most workers will get a better deal than the company could offer, Trader Joe’s said in a statement.