A new study should put to rest any question of whether having health insurance makes a difference for its recipients. This has been a hard question to answer, because people who have insurance and people who don't aren't randomly distributed; there are likely to be other differences between them.

But in 2008, Oregon expanded its Medicaid rolls to include 10,000 previously-uninsured people. Those 10,000 were chosen from 90,000 who applied for the program, leaving 80,000 people who had applied still uninsured. And there were economists on the spot who used this natural experiment to find out what effects insurance has. Quite a lot, as it turns out:

Those with Medicaid were 35 percent more likely to go to a clinic or see a doctor, 15 percent more likely to use prescription drugs and 30 percent more likely to be admitted to a hospital. Researchers were unable to detect a change in emergency room use. Women with insurance were 60 percent more likely to have mammograms, and those with insurance were 20 percent more likely to have their cholesterol checked. They were 70 percent more likely to have a particular clinic or office for medical care and 55 percent more likely to have a doctor whom they usually saw. The insured also felt better: the likelihood that they said their health was good or excellent increased by 25 percent, and they were 40 percent less likely to say that their health had worsened in the past year than those without insurance.

That's a significant improvement in routine preventive care and consistency of care that has the potential to improve health population-wide. And at the same time:

The study found that those with insurance were 25 percent less likely to have an unpaid bill sent to a collection agency and were 40 percent less likely to borrow money or fail to pay other bills because they had to pay medical bills.

Imagine it. You provide people with health insurance and they go to the doctor, get preventive care, and don't go bankrupt because of it. Isn't that how a society should work? Of course, the Republican take on the study will no doubt be outrage that poor people were using their tax dollars for luxuries like mammograms. But meanwhile, for those in power who want to see our society be as productive as possible, here's a tip: if you want a population that's in good health and not burdened by constant financial worries, insuring them is a good start.