Jamie Dimon thinks he knows why people are so gloomy about the economy

• The bottom 20% of American earners have been left out of the economic boom, Jamie Dimon said.
• Their incomes have hardly budged for 20 years, fueling societal problems, the JPMorgan CEO said.
• People can't get a mortgage or afford a home, and communities have been hit by drug abuse and crime.

The US economy may be the envy of the world, but many Americans are deeply discontent. One reason is they've largely missed out on the boom times, Jamie Dimon says.