To hear Donald Trump tell it, the biggest problems with the U.S. economy can be stopped at the border, where immigrants and cheap foreign goods threaten American livelihoods. Or to hear Bernie Sanders tell it, the source of the middle-class's affliction is a powerful Wall Street and K Street oligarchy.
Actually, the forces holding back the economy are internal and structural, the result of historical trends more than venality (I'm talking to you, Bernie), or stupidity (you too, Donald). So they require different solutions from the ones the candidates are pushing.
Perhaps the biggest challenge is that the U.S. labor force is shrinking. Of the richest 38 nations, only the U.S. and two others (Denmark and Norway) have seen declining rates of labor-force participation, which counts the employed and those looking for work.
The unemployment rate has plummeted to 4.9 percent from 10 percent in 2009, but that's largely because people are abandoning the workforce. In 2015, the participation rate fell to its lowest point in almost 40 years. It ticked up in the last few months, but by a barely perceptible amount.