Aggregating and partitioning populations in health care disparities research: differences in perspective.

Health and health care are distributed unevenly across individuals and populations, and identifying these disparities is the first step toward remedying them. We reveal how conceptual and statistical challenges make even the identification of disparities difficult. These difficulties arise because the social, biologic, and environmental causes of disparities are intertwined, leading to statistical confounding. These difficulties arise also because the same data can be analyzed to examine care from the perspective of the patient, or from the perspective of organizations such as health systems or jurisdictions, and these alternative perspectives can yield contradictory results. The result is that health care disparities can be challenging to interpret unless the analytic and policy perspective is clear.