One of the frequently cited effects of having many uninsured folks is that they drive up medical costs by using the ER instead of going to a family doctor or other provider. A new NBER Working Paper by Michael Anderson, Carlos Dobkin, and Tal Gross suggests that this claim is (surprise, surprise) untrue. Here's part of the abstract:

[W]e exploit a sharp change in insurance coverage rates that results from young adults “aging out” of their parents’ insurance plans to estimate the effect of insurance coverage on the utilization of emergency department (ED) and inpatient services. Using the National Health Interview Survey (NHIS) and a census of emergency department records and hospital discharge records from seven states, we find that aging out results in an abrupt 5 to 8 percentage point reduction in the probability of having health insurance. We find that not having insurance leads to a 40 percent reduction in ED visits and a 61 percent reduction in inpatient hospital admissions.