How much should a fast food worker who hasn't finished high school earn? Perhaps half of what a school teacher, who has a B.S. and M.S. earns? A public school teacher averages $39.27/hour or $55.52/hour with benefits. A teacher's average salary is higher than nurses and construction workers, and higher than college teachers per hour with benefits. But would they buy a big mac if those employees made $20/hour? Don't believe me? Scroll down to page 7 of the Bureau of Labor report for the details of your industry. http://www.bls.gov/news.release/pdf/ecec.pdf
The push for higher minimum wage is actually a push to, 1) close industries to punish their owners, 2) move more people to government programs to create more Democratic voters. At $15/hour, many low income workers would lose their government benefits (SNAP, EITC or Medicaid), and they make the same economic choices we all do based on the axiom, "Money talks, it says good-by," and they would probably chose not to work.