TABLE 3

Comparison of California Census Tracts Within Clusters Compared With Census Tracts Outside Clusters (Bivariate Logistic Regression Results)

VariableExemption ClustersPertussis Clusters
OR (95% CI)OR (95% CI)
Population density (100 person/square mile increase)0.99 (0.99–0.99)1.00 (0.99–1.00)
Outside of metro area (compared with inside)2.01 (1.66–2.41)1.27 (1.06–1.52)
Average family size (1 unit increase)0.18 (0.16–0.20)0.44 (0.45–0.53)
Percent nonwhite (1% increase)0.96 (0.95–0.96)0.98 (0.98–0.99)
Percent high school graduates (1% increase)1.06 (1.06–1.07)1.02 (1.02–1.03)
Percent college graduates (1% increase)1.03 (1.03–1.03)1.01 (1.01–1.02)
Percent graduate school graduates (1% increase)1.05 (1.04–1.05)1.03 (1.02–1.04)
Median household income ($10 000 increase)1.12 (1.11–1.14)1.10 (1.08–1.12)
Percent of families in poverty (1% increase)0.95 (0.94–0.95)0.97 (0.97–0.98)
Percent of families with children under age 5 in poverty (1% increase)0.99 (0.99–0.99)0.99 (0.99–1.00)