One-hundred-and-sixty-five years after Marx and Engels penned their cause’s most notorious line, “Workers of the World Unite,” workers in the United States, at least, are anything but unified in a common struggle. Worse, at the beginning of the twenty-first century they are more disunited than they have been since the 1920s, the result of which is the near-extinction of organized labor. Only a paltry 6.9 percent of employees in private industry were unionized as of 2011 (12 percent when public-employee unions were included), down precipitously from a high of 35 percent in the 1950s. Setting aside for the moment the question of whether workers want or need unions in the first place, the disunity of the American labor force has been the subject of much debate in and out of academia. Labor economists and other social scientists have offered a smorgasbord of causes, ranging from technological change and the mobility of workers to the globalization of capitalism, while cheerleaders for the capitalist system cite the obsolescence of unions in the “post-industrial” age. As syndicated columnist George Will proclaimed, “Mobile workers often do not see what value union membership would add to their lives.”