The US economy’s K-shaped recovery is underway. Those with stable full-time jobs, benefits, and a financial cushion are faring well as stock markets climb to new highs. Those who are unemployed or partially employed in low-value-added blue-collar and service jobs - the new “precariat” - are saddled with debt, have little financial wealth, and face diminishing economic prospects.

These trends indicate a growing disconnect between Wall Street and Main Street. The new stock-market highs mean nothing to most people. The bottom 50% of the wealth distribution holds just 0.7% of total equity-market assets, where...