^{Make them pay: They won’t come}

When Kaiser Permanente Medical Group in Oakland, CA, introduced a copayment of $25 or $35 for using the emergency department (ED), the 30,000 enrollees subject to this copayment made 15% fewer ED visits than members of two large control groups not affected by a copayment. Although there was a small decline in the number of visits classified as the most serious conditions, the largest reduction was among those with the least serious conditions. The HMO admitted its ability to determine possible adverse effects of the copayment was limited.