I group these “usual suspects” explanations together for a couple of reasons: First, it is a common and predictable line-up—almost guaranteed to appear, in some order, in most explications of the inequality problem. Second, and more importantly, they share common explanatory problems: 

• Each of these explanations is rooted in broad and global trends (the increased pace and penetration of trade, advances in technology, changes in family composition). As such, they lack much explanatory weight in explaining differences in inequality across national settings—including the outlying case of the United States. 
  
• None of these explanations do a very good job of explaining the timing of increases in wage and income inequality across the last generation—either because the explanatory trends are continuous and the trajectory of inequality is not, or because movement in the explanatory trends do not line up in any chronologically plausible fashion with movement in different kinds inequality. 
  
• Finally, each of these explanations misidentifies—as the key drivers of inequality—broad social and economic trends. Clearly, this is part of the attraction: globalization, technological advances, and demographic change are (each in their own way) inhospitable or inappropriate targets of political intervention. Yet, just as clearly, the differences that actually explain national variations in the pace and timing and character of inequality are not the broad trends, but our political response to them.
  

This last point is the key. It is not as if we are condemned to watching all of this from the sidelines. All of these economic and demographic changes are embedded in a larger institutional and political story. In order to understand U.S. inequality (its growth over time and its exceptionalism), and in order to think about redressing that inequality, we need to focus on “differences that matter.” The simplest way to do this is to go back to our midcentury sketch of the public policies and institutions—the “New Deal order’—that sustained both a floor for the bottom of the labor market and a ceiling for the top of it. What happened to those policies over the last half-century? How did their fate contribute to rising inequality?