| Popis: |
Inspection of maps from the recently-published Atlases of U.S. Cancer Mortality 1,2 suggested that mortality rates for many cancer sites were becoming more geographically homogeneous over time. From 1950 to 1980 rates for the more common tumors (e.g., breast cancer) seemed to increase significantly faster than the overall U.S. rate in areas that had had relatively low rates during the 1950s. We sought to verify this visual impression by quantifying the degree of dispersion of these mortality rates in a manner that would permit comparison of rate variability (a) over time for a particular cancer site, and (b) among cancer sites for the latest time period. It should be emphasized that we were interested in assessing the range or distributional variation of the mortality rates and have not attempted to measure spatial autocorrelation or aggregation. |
