via Jason Furman, RAND has a response (pdf) to claims of attrition. It's quite convincing on the subject of whether cost sharing reduces utilization (it does -- of course it does). So far as whether this fouls the experiment's data on health outcomes in the cost sharing group, the researchers tracked the health of most of those who dropped out of the study, and found that it didn't differ significantly from the experimental group, suggesting that the drop-outs weren't sicker, which would obviate the problem.
