Advancing the study of health inequality: Fundamental causes as systems of exposure.

We tend to study health inequalities as differentials in disease and death that exist a population. But the most important cause of health inequality is social stratification, and social stratification only varies populations. Here, I highlight a way forward in the study of health inequality that resolves this mismatch of analytical levels: we must study the fundamental causes as . Through this critical review of the literature, I argue that the explicit study of variation in social stratification is the next frontier in research on fundamental causes of health inequality.