Response to Invited Commentary Subramanian et al . Respond to ‘ ‘ Think Conceptually , Act Cautiously ’ ’

The importance of socioeconomic position, measured at multiple levels (e.g., individual, household, area) and across the life course, for studying health disparities is now well recognized (1–7). Our multilevel study (8) reported that individual-based socioeconomic measures (IBSMs) and area-based socioeconomic measures (ABSMs) together capture birth weight inequalities that otherwise would have been missed by considering one or the other. We found additionally that, in the absence of IBSMs, the bulk of birth weight disparities captured by ABSMs was approximately similar to that which would have been captured by IBSMs (8). Geronimus (9) critiques these findings, in part, by (mis)interpreting our study as an examination of how well ABSMs serve as ‘‘proxies’’ for IBSMs, even though we explicitly conceptualized ABSMs as capturing some important mix of individualand area-level influences on health, thereby providing valuable information on socioeconomic disparities in health (8). In this rejoinder, we elaborate on the fundamental distinctions between our respective approaches to analyzing socioeconomic disparities in health.