Much has been made in recent years of a volume effect in most aspects of medical care. Evidence for a volume effect has been noted in a variety of surgical procedures and medical treatments. This robust effect has been used both by specialty boards for certification and by third-party payers for reimbursement. It comes as no surprise, therefore, that a volume effect would be seen in the treatment of traumatic brain injuries (TBIs). In the accompanying study by Shi et al.,1 an analysis of all TBIs in Taiwan over a decade-long period yields very similar findings to those seen in other disease entities. Put simply, the more you do, the better you are. Shi and colleagues leverage a countrywide, single-payer system to collect data on all TBIs treated throughout the country over a 12-year period. They find that the volume effect is seen on an institutional level and on an individual surgeon level as well. The strengths of a study like this one are obvious. Data capture in a country that is fairly isolated from its neighbors is likely to be more complete, and less likely to be affected by patient movement to or from its borders. In addition, the existence of a single-payer system means that patients treated within the country are very likely to have data collected into this single system. In countries using a variety of databases and payers, data collection is far more complex and fraught with reliability issues. Data from this study do have their limitations, however. First and foremost, they arise in a health care system very different from the one in the US, and may not be generalizable. Health care delivery in Taiwan may differ sufficiently enough from the US that the distribution of resources between institutions of different sizes may not reflect these resources in countries like the US. It is therefore possible that the smaller medical centers in Taiwan are less able to care for trauma patients in the same manner as they are cared for in the US. Another potential weakness of this type of study is its reliance on the integrity of data collected primarily for budgetary purposes. Unlike the data collected for scientific investigation, the integrity of administrative claims data cannot be vetted for accuracy and may lead to spurious conclusions. The authors attempt to deal with this weakness of the data by restricting their attention to surgical patients. This may result in additional confounders however, because the decision to operate in facilities of different sizes may be different. Finally, the authors of this study suggest that the data support the transport of patients with TBI from lowto high-volume centers. This, of course, is the crux of most volume-based literature. “Centers of excellence” have long been espoused by supporters of the volume-quality effect. What the authors do not address, however, is the potential for morbidity and complications (to say nothing about additional cost) involved in the transport of these acutely ill patients. Patient movement to high-volume centers makes eminent sense in elective medical care; transportation of acutely ill patients who have recently suffered a major TBI may be a lot more complex and risky. The authors of this study should be congratulated for their considerable effort in collecting and analyzing these data, and for their thoughtful interpretation. It clearly adds to the body of evidence supporting a volume effect in everything that we do. Caution must be exercised, however, in interpreting or generalizing their results. (http://thejns.org/doi/abs/10.3171/2012.7.JNS121105)