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Denominator estimation for a hypothetical part of study zone A. The population for those aged 15 through 19 for each tract (P t) is multiplied by the proportion of the tract, or areal weight (A zt/A t), in the study zone. The output for each tract (E pt) in the entire zone is summed to obtain a population estimate for the study zone. Note: For graphic simplicity, only a subset of zones are shown in the figures. Methods are the same for each of the four study zones, A, B, C, and D
