Hisham Uadadeh enrolls in a health insurance plan under the Affordable Care Act on Feb. 13, 2014, in Miami. Rep. Yarmuth: GOP plan takes us back to time before the ACA
Between 6 million and 10 million people would lose health insurance coverage if a Republican proposal to replace the Affordable Care Act becomes law, a new report estimates.
The top end of those losses, or 10 million people, is equal to half of the 20 million or so people who have gained coverage in the past seven years under Obamacare.
The sobering estimate came from S&P Global Ratings on Tuesday, less than a full day after House GOP leaders released their plan for gutting key elements of the ACA, and replacing it with new rules.
S&P Global Ratings said it expected that if the plan were approved, there would be a decline in enrollment in the individual health insurance plan market of between 2 million and 4 million people.
There also would be a decline of between 4 million and 6 million people in the nation's Medicaid system after 2020 to 2024, according to the report.
But profitability among U.S. insurers "will likely improve," the company said, pointing to the fact that the replacement plan "can result in an improved risk pool in the individual market."
The report said that the replacement plan would likely increase the affordability of individual insurance plans for younger adults, and reduce the affordability of those plans "for the older population."
S&P Global Ratings also said it expected there would be a "large difference between states both in terms of insured rates," that is the percentage of people with health coverage, "and benefits covered by insurance plans."
The report is certain to be used by supporters of Obamacare in their efforts to defeat the Republican plan and keep most, if not all, of the ACA intact as the law of the land.
The nonpartisan Congressional Budget Office has yet to "score" the plan, which would analyze both the proposal's costs to the federal government, and its effect on the number of people insured in the United States.
The ACA has been credited with driving down the nation's uninsured rate to record low levels through the creation of government-run marketplaces for individual insurance plans, and by expanding Medicaid eligibility standards to more poor adults than previously were covered.
The GOP proposal calls for ending the ACA rule requiring most Americans to have some form of health coverage or pay a fine. It also calls for replacing Obamacare's system of subsidies for premiums for plans purchased on government-run marketplaces with refundable tax credits that can be used to buy coverage both on and off those marketplaces.
And the proposal would freeze the ACA's expansion of Medicaid benefits to nearly all poor adults in 31 states by 2020, and switch the way the federal government funds the Medicaid programs of states to a block grant system.
This article originally appeared on CNBC. Read more from CNBC: