Alaska and Massachusetts don’t tend to have much in common when it comes to health care, but they do have this: The two spend vastly more per capita on health care than any other state in the country.

Health care spending in the United States ranges from a high of $9,278 per person in Massachusetts to $5,031 in Utah. On average, it hovers at $6,815 per person, a $1,300 increase from just over a decade ago, in 1998.

Income accounts for a lot of it. The cluster of northeastern states with high health care costs also have residents with more income, a factor previous studies have found to correlate with more medical spending. “Eight of the top ten states, including Massachusetts, Connecticut, and New York, are ranked in the top third in the nation for annual personal income per capita,” the researchers note.

But when the researchers really dug into the numbers, they found other factors matter too. States with a higher rate of females between ages 20 and 44, for example, tend to have higher health care costs, likely due to spending associated with pregnancies. Alaska and Maine’s high health care costs are largely driven by high Medicaid costs. The two states spend more on the entitlement program than others. North Dakota - the bright blue state that stands out in the North - remains a bit of a mystery. The state does not have particularly high incomes, nor are its Medicaid enrollment numbers much different from the states around it, although the state’s Medicaid enrollees do tend to be slightly older, presumably coming with higher health care costs.

As for what the low spending states have in common, the researchers settle on one key factor: “relatively younger populations with less access to health insurance.” That leads the researchers to hypothesize these states will see a higher impact from the health reform law’s Medicaid expansion, which will likely extend insurance to more low-income Americans, who disproportionately tend to be a younger population. Come 2014, we’ll likely be looking at a very different map.