A September 2015 poll found that, by a 3-1 margin, voters are more likely to support political candidates who favor raising the minimum wage.

When workers make more money, they respond by being more productive in their jobs and are less likely to leave, reducing turnover costs. This puts money in business' pockets, and workers also then have more money to spend in the local economy.

People decide what markets should do - they are not a force of nature.

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.

The free market hasn't done a very good job "figuring out" how to pay workers enough. If it was solely up to the market, the people with the least power would be paid pennies ... or less.

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.