 In a separate analysis, we will derive a multivariable logistic regression model for quantifying the likelihood that 30-day readmission is avoidable. The development sample will include all cause 30 days readmissions for adult patients hospitalized with CAP. The outcome of interest is a potentially avoidable readmission within 30 days of discharge. We will use only administrative data and the model will be based on combinations of diagnostic codes between the index hospitalization and the readmission. Candidate predictors will be identified by reviewing published models in combination with the opinions of field experts. 