It has been more than 40 years since the level of income inequality in the United States reversed its post–World War II course and began to rise in the late 1970s. Most initial research on the issue, however, was conducted by scholars in economics, industrial relations, and urban planning. It was not until the early 2000s that political scientists and other social scientists started to take up the issue. In the relatively short period of time since then, the field has grown immensely, but political scientists, perhaps not surprisingly, still tend to examine the political causes of rising inequality from either a behavioral or an institutional perspective. The two perspectives are rarely studied simultaneously, and thus the kinds of questions that arise when both types of dynamics are in play have been neglected. Moreover, if I were to hazard a guess as to which of these perspectives has dominated, I would say the behavioral, because (1) the data for behavioral analyses are readily available in public opinion surveys and qualitative interviews; (2) the psychological orientation of virtually all social science research has grown substantially over the past few decades; and (3) the Meltzer and Richard (Journal of Political Economy, 1981) model of median voter preferences for redistribution is the theoretical touchstone in much of the interdisciplinary literature on inequality.

I provide this background because, in some crucial respects, the innovation of Nathan Kelly’s new book is to break through the bifurcated mold of past research, offering what I hope is a harbinger of things to come. I should be clear that Kelly does not himself describe his intentions in exactly this way, and I will suggest that the turning point I am envisioning is not fully realized in the book (or in any book, for that matter). Nonetheless, Kelly’s book provides the ingredients needed for pushing the field of inequality studies forward in productive and transformational ways. I focus here on two aspects of the book that illustrate this potential.

The first is the most transparent, and that is that the book is comprised of two empirical chapters examining the behavioral drivers of inequality and two empirical chapters examining the institutional drivers. In the former chapters, Kelly investigates the most common and widely studied questions in the literature: the reasons why individuals and voters do not support conventional redistributive (tax-and-transfer) polices and liberal (Democratic) candidates in greater numbers in response to rising inequality. What is expected by the median voter model is a majoritarian redistributive response when mean income exceeds median income, but such a response appears lacking. Is it because income inequality itself somehow engenders a reactionary, antigovernment, system-justifying reaction? If so, such a dynamic would suggest that inequality creates a self-reinforcing process, the “inequality trap” of the title.

The first of the two chapters on redistributive preferences (chapter 3) and the second of the two on voting outcomes (chapter 4) do not, however, yield results suggesting that inequality over the decades for which Kelly leverages the available data, from the 1950s to the present, is the main force behind individual and voter preferences, or vice versa. Although he gives it his best shot, he concludes that these factors, and especially public opinion, are “coconspirators rather than the primary culprit” and that “self-reinforcing opinion responses to rising inequality are fairly limited and uncertain” (p. 62).

By contrast, the next two chapters examine two institutional factors that make more of a difference: (1) convergence on inequality-enhancing policy among Democratic and Republican politicians (chapter 5) and (2) status quo bias blocking the passage of popular policies that would reduce inequality (chapter 6). In the behavioral chapters, Kelly insists on the clarity of the choice between Democrats and Republicans to the voter concerned about inequality, but he switches gears in the first of the institutional chapters and provides a qualitative and quantitative assessment of how the Democrats moved toward the center-right in their endorsement of financial deregulation in the late 1990s and potentially of other unpopular policies such as international trade, which had the effect of reinforcing inequality trends. The second of the institutional chapters then shows how policy action to reduce inequality can be stymied by elite and rural capture of undemocratic institutions, especially the Senate (building on an article published with collaborators in Journal of Politics, 2014). This chapter also presents and tests a very useful distinction among different kinds of geographical factors that reduce democratic representation (i.e., gerrymandering and partisan sorting across urban and rural areas).

Although I greatly appreciated the discussion of both behavioral and institutional approaches that Kelly unravels with clarity and in impressive detail throughout these four empirical chapters, he does not address a key question motivating recent interdisciplinary research on the politics of inequality, even though he has the tools to do so at his fingertips: Do the behavioral factors drive the institutional factors, or is the relationship reversed? Is the lack of popular representation demonstrated in the institutional chapters and in other research, along with the neoliberal crippling of social service provision, at the root of voter disarticulation from the political process, leading to protest as one of the only remaining options? Or are psychological processes arising from scarcity of resources and intergroup competition spawning conservative institutional outcomes? Investigating these questions would entail an analysis among the explanatory factors that Kelly instead examines serially in relation to the key outcome of interest, inequality. He does, however, venture into this territory in interesting and speculative ways in the concluding chapter.

This set of considerations leads me to the second way in which the book illustrates how the boundaries of research on the particular issue of rising income inequality are expanding into new and necessary terrain, specifically along the lines urged by the important 2016 American Political Science Association Task Force Report, The Double Bind: The Politics of Racial and Class Inequalities in the Americas, edited by Juliet Hooker and Alvin B. Tillery, Jr. In assessing mechanisms that may explain conservative behavioral responses to rising inequality, Kelly examines racist attitudes among whites as a possible candidate and finds compelling evidence for their role. Of course, a large and increasingly nuanced literature on this topic has blossomed in the Obama and Trump eras (though unfortunately little of it is cited).

What is especially curious to me, however, is the extent to which, in this literature, racial attitudes are typically contrasted to economic concerns (e.g., economic insecurity), and not to rising income inequality per se, as alternative mechanisms explaining support for conservative candidates, particularly among whites without a four-year college degree. Kelly is again very well positioned to explore the exact role of inequality as distinct from, or related to, other economic concerns in the kinds of macro- and multilevel models he employs, but he does not. His sharp analytical focus on inequality is a real asset, and it could have been deployed even further to better understand the political manifestations and intersections of racial and class inequality.

Despite some missed opportunities, Kelly’s book is well written and accessible, yet also subtle and comprehensive in its presentation of the defining political features of contemporary inequality. It should pave the way forward for a new generation of research on inequality that is more expansive than the last.