 Consistent with van Walraven et al. CMAJ 2011;183:e1067-72, four physician reviewers will use a 6-point ordinal scale to rate whether the readmission is an adverse event and whether the adverse event could be avoided. A readmission with a rating above three in both domains will be classified as potentially avoidable by this reviewer. The probability that a readmission is avoidable will be quantified using latent class analysis based on the independent classification by four reviewers. 