From a country founded by settlers and slaves, the United States has grown into a nation of immigrants. The volume Not Just Black and White argues that the arrival of successive immigrant waves—from the not-quite-white ethnics from Southern and Eastern Europe at the turn of the twentieth century, to dark-skinned newcomers from the West Indies and Africa today—has resulted in a repeated redrawing of the color line. At the same time, these immigrants forge new group identities in the United States in reaction to the prevailing black-white divide, leading to, in the words of the volume's editors, “a dialectical interplay between social constructions and interethnic or racial relations” (p. 9).

In exploring this dynamic, half of the essays in this volume take a “then and now” approach, comparing the experiences of various European immigrants at the beginning of the twentieth century to those of Asians and Latinos/Latinas at the century's end. These empirical studies focus on points of contact between groups—from casual networks within immigrant neighborhoods (Richard Alba and Nancy Denton, pp. 237–61) and ethnic businesses (Steven J. Gold, pp. 315–40), to the more intimate connections of family and marriage (Joel Perlmann and Mary C. Waters, pp. 262–77). As with most quantitative history, these essays are interested in documenting the social consequences of existing racial and ethnic categories, not with explaining the shifting salience of the racial categories themselves. The other half of the volume, which is perhaps less familiar to economic historians, explores the historical processes by which these racial and ethnic groupings emerged and changed over time.

The starting point for these contributions, laid out most clearly in a programmatic essay by Stephen Cornell and Douglas Hartmann (pp. 23–41), is that, whereas race and ethnicity are often taken as natural categories—based on the immutable realities of genetics or genealogy—these classifications in fact arise in particular historical contexts. Group identities develop through a combination of self-definition (“who we are”) and external assignment (“who they are, and how they are fundamentally different from us”), and thus change along with the surrounding population (p. 28). Cornell and Hartmann further differentiate ethnicity from race, noting that ethnic identities often develop within a group, whereas racial labels tend to be imposed from the outside. The category “African-American,” then, can be understood as an attempt to superimpose a layer of ethnicity—based on appeals to a common African heritage and a shared contemporary culture—over the “one drop” racial rule historically enforced by the white majority through social convention and Jim Crow legislation.

If racial-ethnic groupings are products of social interactions, how exactly do they grow and change over time? The volume contains little theorizing about the individual- or group-level incentives that encourage group formation, but instead offers a series of case studies. One effective example is Jose Itzigsohn's account of a “situational” pan-Latino/Latina identity that arises within shared neighborhoods and churches and around mutual political aims, but exists alongside still-salient national allegiances. Another is Neil Foley's fascinating history of the landmark court precedents clarifying the racial position of Mexican-Americans, first considered part of the “white race,” later redefined as a “special class” of whites in order to invalidate systematic exclusion from jury service, and finally classified an “identifiable [nonwhite] ethnic-minority group” to prevent school districts from achieving desegregation goals by transferring Mexican-Americans to black schools (pp. 341–57).

Although there is much to be learned from these particular cases, economic historians could add to this conversation by supplementing this historical detail with the comparative tools of economic theory. What are the costs to an individual—in the abstract—of identifying with an ethnic minority, as opposed to “passing” as member of the dominant group, and what are the benefits? What does a group gain in terms of voice or numbers by aligning with other, similar groups, and what does it lose in the specificity of its message? Attention within economics to identity and group formation has expanded greatly in the recent years, with group boundaries variously explained as an internal attempt to ferret out free-riders (Laurence Iannaccone, “Sacrifice and Stigma: Reducing Free-Riding in Cults, Communes, and Other Collectives” Journal of Political Economy 100, no. 2 [1992]: 271–92), or an external product of entrepreneurs sowing group discord (Edward L. Glaeser, “The Political Economy of Hatred.” Quarterly Journal of Economics 120, no. 1 [2005]:45–86). These approaches, or others like them, could be profitably applied to understanding the processes by which formerly racialized immigrants from Southern and Eastern Europe became “white,” the development of pan-ethnic identities at the turn of the century and today, and the durability of the black-white divide.

In the end, the volume raises the implicit question of what implication the theoretical realization that racial and ethnic categories are not reflections of an enduring reality, but instead are social products with histories of their own, should have for empirical historical work. The pragmatic answer may be: none at all. Even if ethnic-racial groups do not reflect actual “genetic or kinship links among persons … what matters is that people think there are such links, and furthermore, that they think those links are important” (Cornell and Hartmann, p. 28). And, as the empirical contributions to the volume substantiate, these groups, no matter how arbitrary, have real implications for individuals' socio-economic outcomes and life chances.

Nevertheless, as Kenneth Prewitt's essay on the history of racial and ethnic categories in the U.S. Census (pp. 145–64) makes clear, markers of group membership in historical data should be used with caveats and caution. Historians must grapple both with the fact that group definitions in the census change over time—for example, Latinos were first identified by their distinctive Spanish surnames and later through self-reported “Hispanic origin”—and, perhaps more seriously, with the time lag between the emergence of a socially salient group and its codification in the census and other survey instruments. For example, the flexibility to identify with multiple racial groups was first allowed only with the 2000 census, despite the long-standing existence of multiracial individuals. Bureaucracies only collect information on a group when its activities begin to interest the government, or when the group itself grows large enough in size or stature to lobby for separate inclusion, as in the case of the multiple race option. In this context, efforts to supplement census data with “local” sources (e.g., the records of emigrant aid societies, the ethnic press) become more important in our understanding of group fortunes.

Prewitt's essay on the racial and ethnic categories in the census would make a good addition to economic history courses, introducing students to the challenges of using the census to study a stable phenomenon over time, as well as to the inherently political nature of its content. And, readers already interested in, say, Latino/Latina integration or immigration law may find the case studies, which are uniformly well written, a valuable resource. As an integrated volume, though, Not Just Black and White is less successful. The conceptual issues it raises—how do racial-ethnic groups form? How do the boundaries between these groups change over time? And how does this fluidity bear on our interpretation of historical data?—are interesting and important ones for economic historians to consider. But, the volume touches on these larger questions only indirectly, thus failing to stake out a theoretical position on the process of identity formation or to suggest new approaches to empirical work in a world of shifting group identities.