TABLE 3.

—Colon Cancer Incidence Rates, Stratified by Area-Based Socioeconomic Measures, Among Persons in Areas With the Least and Most Resources, Along With Age-Adjusted Comparisons (Incidence Rate Ratio and Relative Index of Inequality): Massachusetts, 1987–1993

							Incidence Rate Ratio			Relative Index of Inequality
Selected Area-Based	Rate: Least Resourcesb			Rate: Most Resourcesb			(95% Confidence Interval): Least/Most			(95% Confidence Interval)
Socioeconomic Measurea	BG	CT	ZC	BG	CT	ZC	BG	CT	ZC	BG	CT	ZC
Working class (categorical)	41.3	42.5	41.1	45.8	48.3	27.9	0.90 (0.76, 1.06)	0.88 (0.73, 1.06)	1.47 (1.14, 1.90)	0.89 (0.84, 0.95)	0.85 (0.80, 0.90)	1.28 (1.20, 1.36)
Median household income    (quintile)	41.0	42.5	42.3	46.3	48.9	37.2	0.89 (0.75, 1.04)	0.87 (0.74, 1.03)	1.14 (0.97, 1.34)	0.87 (0.82, 0.93)	0.88 (0.83, 0.93)	1.19 (1.12, 1.27)
Poverty (categorical)	41.7	45.6	44.8	43.9	47.4	41.6	0.95 (0.80, 1.13)	0.96 (0.81, 1.15)	1.08 (0.88, 1.32)	0.94 (0.88, 1.00)	0.95 (0.89, 1.01)	1.06 (0.99, 1.13)
Low education (categorical)	39.5	40.8	43.8	45.2	48.0	39.3	0.87 (0.73, 1.05)	0.85 (0.70, 1.03)	1.11 (0.90, 1.38)	0.84 (0.79, 0.90)	0.90 (0.85, 0.96)	1.15 (1.08, 1.22)
Index of local economic    resources (quintile)	40.3	42.6	43.1	45.4	48.7	33.6	0.89 (0.76, 1.04)	0.87 (0.74, 1.03)	1.28 (1.09, 1.50)	0.86 (0.81, 0.91)	0.88 (0.83, 0.94)	1.27 (1.19, 1.35)

Note. The relative index of inequality is a measure of effect that takes into account both the population distribution of the exposure and the magnitude of the rate ratio detected in each socioeconomic stratum, thereby permitting meaningful comparison of gradients across different socioeconomic measures.25–27 BG = block group; CT = census tract; ZC = zip code.

^aThe area-based socioeconomic measures and their cutpoints for these analyses are defined in Table 4 ▶.17

^bAverage annual rate (per 100 000) age standardized to the year 2000 standard million.28