"Just out of curiosity, with 4.7% unemployment, what pool of employees will go pick onions for $5.15 per hour?"
Probably nobody, which means they have to pay more. How many doctors would work for 25,000 dollars a year? None, so we pay them 250,000. If nobody wants to pick tomatoes at 5.15, pay them 10. If you divide 4.85 over a couple hundred tomatoes we'll pay maybe a penny or two more for a tomatoes, and pay thousands less a year for immigrants who drain our welfare state.