The "Using real life crash data" section is just wrong. The IIHS confidence interval describes an empirical death rate, not an "expected fatality rate." Therefo

The "Using real life crash data" section is just wrong. The IIHS confidence interval describes an empirical death rate, not an "expected fatality rate." Therefore, an interval including 0 deaths per million registered vehicle years arises due to very few deaths over a very large dataset, not from some "informative prior" bounding the interval at 0. As an empirical description, the IIHS figures should have high statistical power, after adjusting for confounding variables. Time and location could be interesting factors to consider. For Dan's suggestions, the IIHS already breaks down death rates per 10 billion miles by vehicle class and individual vehicles, and the latter supports the original ordering by registered vehicle years. Also, incorporating data from models under the same make doesn't make sense. Since the IIHS already accounts for different vehicle platforms, any believed correlation in death rates between a manufacturer's models must derive from the original dataset, creating a meaningless statistic. Updated IIHS doc here: https://www.iihs.org/api/datastoredocument/status-report/pdf/55/2 https://www.iihs.org/api/datastoredocument/status-report/pdf...