A trillion here, a trillion there, and pretty soon you're talking about real money. The United States is on track to spend $2.6 trillion less on health care over a five-year period than was originally projected after the passage of Obamacare, a new Urban Institute study released Monday said. The report also said there is evidence that the growth in health spending has again slowed after it spiked in 2014.

It remains an open question whether Obamacare itself is responsible for the slowdown in estimated spending from 2014-19, which represents an 11 percent drop in spending estimates, or whether the overall sluggish economy should get the credit. The Urban Institute report said that if the savings end up being due to Obamacare, "then slower growth [in national health spending] may persist beyond current projections." "But if the economy was the primary driver of slower growth, then we should expect a return to faster growth with a robust recovery," according to the report, which relies on data from the federal Centers for Medicare and Medicaid Services, and which was funded by the Robert Wood Johnson Foundation.

In 2010, when the Affordable Care Act became law, federal health regulators estimated that national health spending would top $4.614 trillion by 2019, the report noted. But now that year is expected to see just $4.02 trillion in health spending — a difference of more than $600 billion, according to the report. And from 2014 through 2019, the cumulative difference between what is now expected will be $2.6 trillion lower than what was originally projected in 2010 for the same time period, according to the Urban Institute. The report broke down the factors that are contributing to that dramatic slowdown. Spending on Medicaid — the joint federal-state health program for the poor — will be $1.05 trillion lower than originally projected during the time span, a 23 percent difference. "This was partly due to the Supreme Court decision in 2012 that made ACA Medicaid expansion optional for states and significantly reduced enrollment projections," the report said.