Understanding Variations in Group Differences that are the Results of Variations in the Prevalence of an Outcome American Public Health Association 134 th Annual Meeting & Exposition, Nov. 4-8, 2006, Boston, MA James P. Scanlan Attorney at Law Washington, DC

Interpretive Rule (IR1) 1 When two groups differ in their susceptibility to an outcome, the rarer the outcome, (a) the greater the relative difference in rates of experiencing it, and (b) the smaller the relative difference in rates of avoiding it.

Implications of IR1 Health Disparities Research Interpretation of Differential Effects of Ameliorative and Exacerbating Factors

References available on jpscanlan.com “Can We Actually Measure Health Disparities?” Chance (Spring 2006) “Race and Mortality,” Society (Jan-Feb 2000) “The Misinterpretation of Health Inequalites in the United Kingdon,” British Society for Populations Studies Annual Conference (2006) “The Misintrepretation of Health Inequalities in Nordic Countries,” 5 th Nordic Health Promotion Research Conference (2006)

Table 1: Blacks and Whites Below Two Income Levels Percentage of Poverty Line (a) Black Perc of BW Pop Below (b) Black/White Ratio Below (c)

Fig. 1 Adverse Outcome Ratios Based on Income Data Ratio of Black Rate to White Rate of Falling Below Each of 12 Income Levels

Text Description of Figure 1 Figure 1 shows the ratio of the black rate to the white rate of falling below each of 12 income levels defined by percentages of the poverty line, ranging from 600 percent to 50 percent of the poverty line. As the percentage of the poverty line declines, the black-white ratio of falling below it increases.

Fig 2: Favorable Outcome Ratios Based on Income Data Ratio of White Rate to Black Rate of Falling Above Each of 12 Income Levels

Text Description of Figure 2 Figure 2 shows the ratio of the white rate to the black rate of falling above each of 12 points defined by percentages of the poverty line, ranging from 600 percent to 50 percent of the poverty line. As the percentage of the poverty line declines, the white-black ratio of falling above it decreases.

Health Disparity Research Implications of IR 1 The perception that disparities are increasing The appraisal of the size of disparities – Larger disparities among the young than the old – Large racial differences in infant mortality where parent are highly educated – Large SES mortality differences among British civil servants (see British Society for Pop Studies) – Large SES mortality differences in Norway and Sweden (see Nordic Health Promotion Conf presentation)

Differential Effects Implications of IR1 Exacerbating factors (e.g., obesity, smoking, etc.) would be expected to increase adverse outcomes more among the least susceptible groups (e.g., whites, women, the young, non- smokers), but reduce favorable outcomes more among the most susceptible groups Beneficial interventions would be expected to reduce adverse outcomes more among the least susceptible groups, but increase favorable outcomes more among the most susceptible groups.