A half century ago America’s largest private-sector employer was General Motors, whose full-time workers earned an average hourly wage of around $50, in today’s dollars, including health and pension benefits.

Today, America’s largest employer is Walmart, whose average employee earns $8.81 an hour. A third of Walmart’s employees work less than 28 hours per week and don’t qualify for benefits.

There are many reasons for the difference – including globalization and technological changes that have shrunk employment in American manufacturing while enlarging it in sectors involving personal services, such as retail.

But one reason, closely related to this seismic shift, is the decline of labor unions in the United States. In the 1950s, over a third of private-sector workers belonged to a union. Today fewer than 7 percent do. As a result, the typical American worker no longer has the bargaining clout to get a sizeable share of corporate profits.

At the peak of its power and influence in the 1950s, the United Auto Workers could claim a significant portion of GM’s earnings for its members.

Walmart’s employees, by contrast, have no union to represent them. So they’ve had no means of getting much of the corporation’s earnings.