We interpret overlapping confidence intervals as evidence of lack of a significant difference. Parametric and non-parametric exact tests will be used as appropriate, with 95% confidence intervals and a 5% significance level. Our main analysis will be a complete case analysis, in which we exclude observations with missing values in any of the following variables: age, sex, mechanism of injury, transfer status, and outcome. Observations with no injuries reported will be assigned an ICISS of 1 and for each observation the final ICISS will be calculated based only on SRR for ICD-codes that occurred in at least 10 observations in the derivation sample.