WASHINGTON (TIP): The Obama administration has said that 6.3 million people were determined to be eligible for Medicaid between October and December.

But the study, from health-care industry consulting firm Avalere Health, suggests that only a fraction of the enrollments are strictly the result of the health-care law, according to a news report in Washington Post.

The study reveals that between 1 million and 2 million Americans signed up for Medicaid last year because of the health-care law, suggesting that many of the people who have joined the program since the initiative’s rollout in October would have done so absent the law.

The study is the latest effort by industry experts to dive into the enrollment numbers that have been released by the Obama administration. The administration’s figures have done little to illuminate whether the law is accomplishing one of its chief goals: reducing the ranks of the uninsured in America.

The new report shows that the administration has an uphill climb, said Caroline Pearson, vice president of Avalere. “One major goal of the [Affordable Care Act] was to reduce the number of uninsured, and Medicaid expansion is a key part of that,” she said. “These numbers show that the administration has a ways to go toward its enrollment goal and will need to conduct sustained outreach and education efforts to draw more people into coverage throughout the year.”

The Medicaid figures have been a source of controversy since the Obama administration began releasing private health insurance enrollment data and Medicaid eligibility figures. The administration has said that its 6.3 million figure is incomplete and includes renewals. Nevertheless, the administration has used the number – along with statistics showing that 3 million people signed up for private plans and a similar number benefited from a rule allowing young adults to stay on their parents’ health plans – to show that the health law is succeeding.

“Already, because of the Affordable Care Act, more than 3 million Americans under age 26 have gained coverage under their parents’ plans,” President Obama said in his State of the Union address last month. “More than 9 million Americans have signed up for private health insurance or Medicaid coverage – 9 million.” Asked Wednesday, February 5 by WAMU radio host Diane Rehm how he responds to persistent criticism of the health-care law, Labor Secretary Thomas Perez said: “I think we overcome that with the facts,” citing as one fact that “6 million are enrolled through Medicaid expansion.”

Joanne Peters, a spokeswoman for the Department of Health and Human Services, declined to address the specific details in the Avalere report. “We’re thrilled that since October, millions of Americans have enrolled in health insurance coverage,” she said in a statement. “Three million people have signed up for private plans in the Marketplace and more than 6 million learned they were eligible for Medicaid and CHIP [the Children’s Health Insurance Program], including new determinations in states expanding coverage as well as those made based on prior law and renewals.”

It’s also hard to pin down how many people who bought private health plans via the new online marketplaces were previously uninsured. A McKinsey & Co. survey of 4,563 consumers eligible to enroll in private plans found that only 11 percent of individuals who bought new coverage were previously uninsured in 2013. For its analysis, Avalere compared the Medicaid enrollment numbers reported by the administration to the average monthly number of applications submitted over three months last summer.

It estimated that between 1.1 million and 1.8 million people signed up for Medicaid through December because of the health law. That includes people who became newly eligible for the program because of the Medicaid expansion, as well as those who already were eligible but signed up only after the law got so much publicity. The rest of the enrollees, Avalere determined, were part of the typical flow of people who go on and off programs as their incomes and life circumstances change. Some Medicaid experts were skeptical of Avalere’s conclusion because it didn’t take seasonal variations into consideration.

During the summer months, “we tend to have an influx of farm workers who are temporarily on Medicaid,” said Diane Rowland, executive vice president of the Kaiser Family Foundation. In addition, Rowland said, the study uses new and incomplete data. Some states count the number of individuals who sign up, while other states count applications, which may include four or five people. But Judith Solomon, vice president of health policy at the Center on Budget and Policy Priorities, said the Avalere figure is probably more accurate than the number put forward by the administration.