Another issue in the longitudinal tracking of performance is compensating for general trends in care. Several studies have reported on global reductions in hospital mortality over time.10,11 Although there are no ICU-specific data, the recalibration of the APACHE algorithms provides some helpful insights.3,4 The APACHE III algorithms, when applied to the APACHE IV reference population, generated a hospital SMR of 0.93, suggesting that mortality decreased by slightly less than 1% a year over the 10 years between the two calibrations.3 Our group performed a similar comparison for LOS performance using the eRI data set and observed negligible difference in the actual-to-predicted ratios, suggesting little change in LOS performance over the same interval. Although these data suggest that time-related changes in ICU performance have been small over the past decade, larger changes in aggregate performance may be seen in the future. Specifically, the current focus on quality improvement and cost reduction, the introduction of new therapeutic approaches to several high-impact diseases (eg, severe sepsis), and the implementation of new ICU care models may accelerate future improvements.12-14 In order to compensate for temporal trends, scoring systems need periodic recalibration; the CalHospitalCompare (California Intensive Care Outcomes) project is considering yearly updates of their algorithms (R. Adams Dudley, MD, oral communication, December 2010). Although regular recalibration is necessary to ensure that ICU outcomes are not compared with an old reference population that used therapies and practices that are different from those in current use, it is equally important to track ICU performance trends by referencing newly calibrated systems to their predecessors, and making this information available to consumers of public health information.