The predictive validity of this measure has been previously established (23, 24) and has been identified as a superior approach than measures of staffing from administrative databases (24, 25). A mean critical care staffing measure for each hospital was generated from nurses who reported caring for at least one but less than seven patients on their last shift. Reports from nurses who cared for seven patients or more (represented < 1% of the respondents) were excluded from the calculation of the mean staffing measure since we suspected that such nurses were not likely to represent bedside critical care nurses. The ICC for the critical care staffing measure using a minimum of five nurse respondents per hospital in this study was 0.65, which is above the generally accepted level of 0.60 for aggregated data