In the wake of the police shooting and charged protests that unfolded in Ferguson, Missouri in August, Kareem Abdul-Jabbar argued in TIME that despite the persistence of racial inequality in the U.S., class is quickly becoming the most significant measure of disadvantage. “This fist-shaking of everyone’s racial agenda distracts America from the larger issue that the targets of police overreaction are based less on skin color and more on an even worse Ebola-level affliction: being poor,” Abdul-Jabbar wrote.

Is class in fact replacing race as the great divider in the U.S.? A new book from the Russell Sage Foundation by Douglas S. Massey and Stefanie Brodmann, Spheres of Influence: The Social Ecology of Racial and Class Inequality, investigates this claim. The authors trace how the civil rights movement, the increase in immigration from Asia and Latin America, and the restructuring of the economy in favor of the rich over the last several decades have begun to alter the contours of inequality in the U.S. They show that rather than operating in isolation, race and class are increasingly interacting in complex ways in order to produce and reproduce disadvantage for certain groups.

In their chapter “Divergent Family Spheres,” Massey and Brodmann investigate how race-class interactions affect different families’ access to material, emotional, and symbolic resources. To analyze these interactions, they first present idealized distributions that isolate pure race and class effects, ranking sixteen race-class categories in ascending order of disadvantage. (In the following graphs, BLO refers to the black lower class, BLM to the black lower middle class, BUM to the black upper middle class, and BUP to the black upper class. The other codes substitute W, A, and H to indicate class categories for whites, Asians, and Hispanics.)

These stylized distributions illustrate the effects of race and class separately from each other. For example, in the “pure race effect” graph, all blacks, regardless of class, are ranked equally at the disadvantaged end of the spectrum. Conversely, in the “pure class effect” graph, all lower class groups, regardless of race, are positioned as equally disadvantaged:

Yet, as Massey and Brodmann show, when race and class intersect, the resulting distributions deviate in varying degrees from these idealized graphs. Looking at average household income, the authors find that the effects of racial inequality are exacerbated by the class differences within racial groups. Though within-class differences are not large, African Americans occupy the lowest position in each quadrant, showing that race continues to stratify groups even within the same economic class:

Massey and Brodmann find even more significant interactions between race and class when analyzing different groups’ access to health care. Upper-class blacks were only 70% likely to have health insurance, as opposed to 75% of upper-class whites and 85% of upper-class Asians. Upper-class Hispanics ranked even lower for insurance coverage, at about 62%. Similarly, at the other end of the class spectrum, lower-class blacks and Hispanics were again much less likely to have health insurance than their white and Asian counterparts:

In other words, although class certainly is a major factor in determining one’s access to health care, Figure 2.3 illustrates the continuing significance of race in health insurance coverage.

Spheres of Influence further explores race-class interactions in areas such as education, occupational status, and incarceration. By advancing an ecological model of human development that considers the dynamics of race and class across multiple social spheres, Massey and Brodmann shed important light on the factors that are currently driving inequality today.

Click here to read more about Spheres of Influence, download other tables and figures, or purchase a copy of the book.