With immigration at the forefront of national debate, Jim Stimpson decided it was time to do a little more digging.

“There’s a lot of rhetoric around immigrants’ use of public services in general and health care specifically, and I thought with impending federal immigration reform it would be useful to have some sort of contribution about the facts of unauthorized immigrants’ use of health services in the United States,” said Stimpson, a professor within the University of Nebraska’s School of Public Health and director of the university’s Center for Health Policy.

So together with colleagues Fernando Wilson and Dejun Su, Stimpson studied the differences in health care spending between U.S. natives and immigrants of different legal status. They found that unauthorized, legal and naturalized immigrants together accounted for $96.5 billion in average annual health care spending, while U.S. natives accounted for slightly more than $1 trillion. Unauthorized immigrants had the smallest share of health care spending at $15.4 billion — this amount includes money they spent out of their pockets as well as money from public health care sources and private insurance payments and does not include uncompensated care costs. To gather their findings, researchers studied data from the Medical Expenditure Panel Survey from 2000 to 2009.

Stimpson told me the findings, which were published this month in Health Affairs, weren’t necessarily a surprise.

“The findings were very consistent with a lot of other literature on immigrants,” he said. “We generally find that immigrants have lower health care use and spending than U.S. natives and when you dig even deeper, you find that recent immigrants have even lower uses and expenses than immigrants who have been here longer. Clearly, (unauthorized immigrants) have, by far and away, the least amount of utilization.”

The study researchers also found that just 7.9 percent of unauthorized immigrants benefited from public-sector health care spending, compared to 30.1 percent of U.S. natives. However, unauthorized immigrants were more than twice as likely to receive uncompensated care than U.S. natives, which is not surprising as such immigrants are more likely to go uninsured and face multiple barriers to gaining insurance coverage.

Stimpson noted the “selection effect” when citing unauthorized immigrants’ lower use of health care services and lower spending. In other words, he said unauthorized immigrants coming into the country looking for job and economic opportunities tend to be healthy and able-bodied — “it takes a lot of gumption to come to the U.S. … for example, an immigrant coming here from Mexico isn’t necessarily representative of (overall health status) in Mexico.” On the topic, the study researchers wrote:

…healthy people migrate to the United States and stay in the country longer, while unhealthy people do not migrate at all or stay for shorter periods, returning to their country of origin. Other studies have shown that immigrants lose their health advantage over time and begin to have health profiles similar to those of U.S. natives. Our results are consistent with these hypotheses because we found a stepped relationship between spending and level of acculturation: U.S. natives spent the most on health care, naturalized citizens spent nearly as much as U.S. natives, and unauthorized immigrants spent the least.

The findings have a number of implications for policy discussions (and unfounded fears) around immigrants’ use of public services and health care, in particular. Currently, unauthorized immigrants are barred from participating in the state-based health insurance exchanges created via the Affordable Care Act, and even legal immigrants have very few options for obtaining affordable coverage and don’t qualify for Medicaid or the Children’s Health Insurance Program if they’ve been in the country for less than five years. And while some policymakers and advocates claim that unauthorized immigrants drain public resources, they actually end up putting a lot more money into the system than they use, Stimpson said.

For example, he cited another recent study published in Health Affairs that found that immigrants disproportionately subsidize the Medicare Trust Fund. That study showed that in 2009, immigrants made 14.7 percent of trust fund contributions but accounted for only about 8 percent of its expenditures — a net surplus of $13.8 billion. On the other hand, U.S. natives generated a $30.9 billion deficit.

According to Stimpson, it would be to the nation’s benefit to open up the state health insurance exchanges — which are set to launch open enrollment in October — to unauthorized immigrants. He noted that as his study found that unauthorized immigrants pay a high proportion of their health care expenses out of pocket, it might suggest that many would purchase affordable private insurance if they had the opportunity.

“This is the kind of population you want (in the exchanges) because they’ll put a lot more money in than they take out,” he said. “It’s a young, healthy population and one of the goals of the ACA is to get younger people to join (the overall risk pool).”

To access a full copy of the Health Affairs study, click here. To learn more about immigrants and the Affordable Care Act, visit the National Immigration Law Center.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.