Found the study -- it's by Blalock, Garrick, Vrinda, Kadiyali and Simon, and published in the Journal of Law and Economics, November 2007. The authors' analysis demonstrates that every 1 million trips shifted from air to road travel results, on average, in 15 incremental deaths. By controlling for other factors -- weather, economics, etc. -- the authors were able to calculate the number of trips shifted from air to surface travel as a result of TSA harassment, and then apply the mortality factor to conclude that approximately 500 deaths a year are attributable to the TSA. In contrast, an average of about 18 deaths a year are attributable to air travel related terrorist activities in the USA. It can, of course, be debated if it's actually 400 or 600 rather than 500, but it is not possible to reasonably contest the fact that the TSA is responsible for a significant net increase in mortality rates.