To the Editor Understanding out-of-pocket spending is critical to understanding health care costs in the United States. We applaud the efforts of Adrion et al as an important contribution to understanding the out-of-pocket spending of the commercially insured population younger than 65 years. The commercially insured comprise over 50% of the nonelderly US population and, as demonstrated by Adrion et al, out-of-pocket spending on inpatient services can be substantial.