Spending on emergency department (ED) facility fees rose steadily between 2009 and 2015, even as the overall number of ED fees billed declined, according to an analysis of Health Care Cost Institute (HCCI) data, Sarah Kliff writes for Vox. However, the American College of Emergency Physicians (ACEP) is pushing back against the findings, noting that the analysis examined only spending by employer-sponsored health insurance plans.

The analysis is part of a yearlong investigation by Kliff into a charge commonly called an "emergency facility fee"—a base fee most hospitals charge for any ED service. According to Vox, the fees generally are not publicly shared and vary widely by hospital.

For the latest analysis, Vox collaborated with HCCI to analyze 70 million insurance bills from employer-sponsored plans for ED visits between 2009 and 2015. The analysis focused on the prices health plans actually paid hospital EDs for facility fees instead of the hospital's charges, which Vox reports often are higher than the amount ultimately paid.