Seeking to draw attention away from the fiasco that Obamacare has become and shore up his flagging popularity, President Obama recently pivoted yet again to a message of economic populism that included calling for a minimum wage increase.

"There’s no solid evidence that a higher minimum wage costs jobs, and research shows it raises incomes for low-wage workers and boosts short-term economic growth," he said.

Advocates want the minimum wage raised to $15 from $7.25. But if it's such a boost to economic growth, why not raise it to $30, or more? Why stop at $15?