Centers for Disease Control and Prevention National Center for Health Statistics

1. Is Disparity Getting Smaller? Ken Keppel, Ph.D. Centers for Disease Control and Prevention National Center for Health Statistics

2. How did the disparity in infant mortality rates for black non-Hispanic women change during the last decade?

3. What is the reference point? • Another group rate (White non-Hispanic women, for example) • The “best” group rate (Asian or Pacific Islander women) • The average of race/origin group rates • The total infant mortality rate • The Healthy People 2000 target

4. Simple difference Percent difference Ratio Simple difference/target Ratio of percent change Which statistic should we use? Absolute Relative

5. Simple Difference: ri - rrpWhere: ri is the rate for group i, and rrp is the rate for the reference point.Percent difference: (ri - rrp) / rrp * 100Where: ri is the rate for group i, and rrp is the rate for the reference point.Ratio: ri / rrpWhere: ri is the rate for group i, and rrp is the rate for the reference point.Simple difference/target: ( ri - rrp ) / TWhere: ri is the rate for group i, rrp is the rate for the reference point, and T is a target.Ratio of percent change: {(rrp,1 - rrp,0) / rrp,0} / {(ri,1 - ri,0) / ri,0}Where: rrp,1 is the rate at time one for the reference point, rrp,0 is the rate at time zero for the reference point, ri,1 is the rate at time one for group i, ri,0 is the rate at time zero for group i.

6. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

7. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

8. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

9. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

10. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

12. How did the disparity in infant mortality rates among race/origin groups change during the last decade?

13. What is the reference point? • Another group rate (White non-Hispanic women, for example) • The “best” group rate (Asian or Pacific Islander women) • The average of race/origin group rates • The total infant mortality rate • The Healthy People 2000 target

14. Source: CDC, National Vital Statistics System, Linked birth/infant death data set

18. Range Mean deviation Mean deviation/reference point Mean deviation/target Average of ratios Which statistic should we use? Absolute Relative

19. Range: rmaximum – rminimumWhere: rmaximum is the rate in the group with the highest rate, and rminimum is the rate in the group with the lowest rate.Mean deviation: 3ni=1*ri – rrp*/ nWhere: ri is the rate in group i, rrp is the rate for the reference point, and n is the number of groups or the number of groups minus 1 if one of the groups is the reference point.Mean deviation/reference point: (3ni=1*ri – rrp*/ n) / rrpWhere: ri is the rate in group i, rrp is the rate for the reference point, and n is the number of groups or the number of groups minus 1 if one of the groups is the reference point.Mean deviation/target: (3ni=1*ri – rrp*/ n) / TWhere: ri is the rate in group i, rrp is the rate for the reference point, n is the number of groups or the number of groups minus 1 if one of the groups is the reference point, and T is a target.Average of ratios: [3ni=1 |(ri / rrp) - 1 |] / nWhere: ri is the rate in groups i, and rrp is the rate for the reference point , and n is the number of groups or the number of groups minus 1 if one of the groups is the reference point.

21. Conclusions about change in disparity for a particular group and change in disparity among several groups depend on • Which reference point is chosen for comparison • Whether an absolute or a relative comparison is made • Which statistic is used to make the comparison

22. We should operationalize our measurement of disparity in terms of what we really mean when we say that our goal is to eliminate disparities among subgroups in the population.