Monitoring change in health disparity.

Agencies and programs tasked to reduce and eliminate disparity need the best available methods to assess the success of their efforts. When monitoring disparity it is vital to be aware of how absolute and relative measures of disparity, and when changes are measured, can lead to different conclusions regarding progress. Absolute and relative disparities for homicide rates between Hispanics and non-Hispanic Whites were calculated on an annual basis for 1989 through 2003. A joinpoint regression of rates was used to identify where significant changes occurred over the 15-year period. Absolute and relative changes in disparity were measured for each interval identified. The annualized percent changes in homicide rates for each interval were used to evaluate how relative rates of change in homicide affect disparity. Three distinct change points were found for homicide rates and changes in disparity between Hispanics and non-Hispanic Whites for the period 1989-2003. Intervals 2 (1991-1994) and 3 (1994-1999) had declines in both absolute and relative disparity. Only interval 3 had disparity reductions sufficient, if they had continued, to suggest any elimination of disparity within the next 5 years. Reduction in the relative difference between groups is the best evidence of progress toward eliminating disparity. The relative rate of improvement for the group with less favorable rate must be greater than that of the group with the more favorable rate. It is just as important to be aware of when disparity is being assessed in a longer overall trend.