Table 2.

Proportion of variance in Ln(BLL–0.5) from the Michigan Department of Community Health database, explained by dichotomized zip code risk, zip code, census tract, and block group by four-year period^a

^aFor the years 1998–2001, all analyses are based on approximately 220,000 cases. For the years 2002–2005, all analyses are based on approximately 340,000 cases. In each analysis, the geographic unit was the sole predictor.

Ln = logarithm

BLL = blood lead level