Some hospitals say they can separate the law's impact on profits from those of the improving economy, which also helps people get more access to health care and makes them more willing to pay for their own share of discretionary procedures.
The ACA's impact is about the same as the effect of a better economy, said Universal Health Services CFO Steve Filton. Each was responsible for about 35 percent to 40 percent of the company's gain in profit this quarter.
"It certainly appears as if the growth rate that we realized in the third quarter … was still very strong," Filton said, though he added that growth was even greater in the second quarter. "This seems to us to be sort of a more sustainable rate going forward."
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LifePoint received a bigger bump from the ACA than some rivals, because rural communities it serves have seen a less-robust recovery this year than urban markets, where HCA, Tenet and Community have a bigger presence, said Jefferies analyst Brian Tanquilut.
Obamacare's impact can also be seen in the wider profit margins that hospital chains have reported. Because the law is designed to contain costs as well as give insurance to more people, hospitals and other health-care providers are merging to build up scale.
"We have had a lot of overcapacity in hospitals," Tanquilut said. "You don't have to hire many more nurses if you raise occupancy. And hospitals have been buying medical devices at better prices because they are bigger."
On Monday, Franklin, Tennessee-based Community Health Systems said it earned $62 million, or 54 cents a share, on third-quarter sales of $4.8 billion that, like Tenet's, were boosted by a merger.
Between them, the five major hospital chains own or manage 534 U.S. hospitals, according to their federal securities filings. That's half of the 1,068 for-profit U.S. hospitals reported by the American Hospital Association.