The researchers are developing prior work on the temporal, spatial and socioeconomic variation in US mortality for males and females. To achieve these goals they will assemble a data set of time series of mortality rates by age, cause and sex, and assemble a data set of relevant socio-economic and environmental variables for all US counties starting in 1970. Data set assembly now nearly complete, code for county-level comparisons of variance written and tested, and a new focus on male-female comparisons, so far mainly done with international data. International analyses are the first to causally demonstrate that changes in causes of death that are strongly influenced by tobacco use are responsible for the change in the female-male difference in life expectancy. These results are one of the few that demonstrate, at whole-country population level, the impact of a single public health change. Further, the study makes novel use of high-quality demographic data, cause-of-death data curated by WHO, and decompositions of mortality rates that have rarely been used in epidemiologic or public health literature.