In Reply Our study1 on inequalities in life expectancy found that a combination of socioeconomic and race/ethnicity factors, behavioral and metabolic risk factors, and health care factors could explain 74% of the variation in life expectancy among counties. We agree with Dr Mestral that other factors such as diet quality and housing conditions may play a role in explaining the remaining variation. This is an important area of future research and will require identifying appropriate county-level data sources that relate to these factors.