The socioeconomic stratification that patterns American life, and differences in life for the major racial/ethnic groups, is assumed to be the root cause of these differences (Adler et al., 1994; Link and Phelan, 1995). People of different social statuses lead lives that differ in almost all aspects—childhood circumstances, educational experiences, work careers, marriage and family experiences, leisure, neighborhood conditions, and health care (Williams and Collins, 1995). Many of the effects of SES on health outcomes are indirect through a variety of life experiences, opportunities, or choices related to SES, beginning in early life and either cumulating or being tempered by later life situations. Health differences are observed throughout the lifecycle, and the general assumption is that differences diminish at older ages. This assumption was questioned recently by Lynch (2003).

Socioeconomic status is obviously related to race and ethnicity in the United States, but the role of socioeconomic factors as a cause of racial/ ethnic health differences is complex. Many studies have documented the importance of blacks’ low SES as a partial explanation for poor health outcomes relative to whites. Studies have also clarified that socioeconomic differences often do not “explain” all health differences between African Americans and non-Hispanic whites, with black-white differences in health remaining after controlling for socioeconomic conditions (Hayward et al., 2000). Asian Americans’ comparatively high SES has been suggested as a cause of this group’s better health, but again, other factors also appear to come into play (Lauderdale and Kestenbaum, 2002). The “Hispanic paradox,” or the better than expected health experienced by the socioeconomically disadvantaged Hispanic population, is another example of the complexity of the relationships among race/ethnicity, SES, and health outcomes (Abraido-Lanza, Dohrenwend, Ng-Mak, and Turner, 1999).

Ambiguity also surrounds the mechanisms through which SES promotes racial/ethnic differences in health. The issue of whether members of all ethnic groups are able to equally translate increases in SES into health improvements has been raised (Ribisi, Winkleby, Fortmann, and Fiora, 1998; Williams, Lavizzo-Mourey, and Warren, 1994). In addition, researchers have questioned whether the race gap in health is concentrated at the low end of the socioeconomic ladder, with some studies reporting that the race gap in health is strongest among persons with the fewest socioeconomic resources (Lillie-Blanton, Parsons, Gayle, and Dievler, 1996). Other researchers have suggested that the association is more linear, with increasingly better health as SES increases, although there may be some leveling off at the top (Adler et al., 1993; House, Kessler, and Herzog, 1990; Pappas et al., 1993).

Both health and socioeconomic status have many dimensions and can be conceptualized and measured in multiple ways, with measurement often