Fig. 3

Geographic centroid assignment. Each county centroid is attributed a county mortality count for the population of interest. Mortality counts for centroids falling within each study zone are summed to estimate mortality, as a whole number, by zone. In this hypothetical example, zones A and B are assigned zero deaths, despite the overlap of three counties on zone A (two potential deaths) and five on zone B (four potential deaths). Zone C is assigned four deaths, but has the possibility of more