Annual earnings in the fast-food industry are well below the income needed for self-sufficiency, and fast-food industry jobs are also much less likely than other jobs to provide health benefits.

When families can afford the basics, they can reinvest in their communities, and higher wages means a broader consumer base for businesses.

Most fast-food workers can't easily join a union, because they don't work directly for their parent company, such as McDonald's or Subway. Instead, they work for individual franchise owners, ensuring that each individual fast-food outlet would have to organize and win union recognition separately. So there's not one central employer to bargain with, as in a traditional union campaign.

Fast food also has a uniquely difficult business structure for workers to achieve better wages and working conditions.

The minimum wage isn't earned only by people working at fast food restaurants and in service industry work - the average income for positions like nursing assistants, preschool teachers and paramedics are all under $15.

We've created more wealth in the past 30 years than the rest of human of human history combined. But half of Americans make less than $17 an hour.

Income inequality and wage stagnation finally took their place among the principal moral issues of our time.