In the future of automation, the crisis in the advanced economies may be flat wages and not a lack of jobs. That future appears already to be here: In April, unemployment fell to 3.9%, but two-thirds of U.S. jobs pay less than $20 an hour. And the three most-common jobs, held by 11.5 million people, pay much less.

Retail sales ($13.07 an hour)

($13.07 an hour) Cashier ($10.43)

($10.43) Food-preparer ($9.84)

Why it matters: In the first technological cycle of the Industrial Age, in the beginning of the 19th century, we got the Luddite uprising. Over the subsequent decades, jobs were destroyed and new jobs created, roiling millions of people's lives. But the biggest crisis was low wages — Americans could not afford the basics.

It took until around the 1880s for average wages to rebalance.

the 1880s for average wages to rebalance. But by then, widespread inequality had triggered a global political crisis very much resembling today's (for more, read Barbara Tuchman's The Proud Tower. h/t Karen Harris)

Today, many teachers are in the group that can't afford the basics: Near the high end of the United Way survey are elementary school teachers, earning an average of $29.51 an hour.

Axios' Michael Sykes writes today that, as part of a wave across the country, North Carolina teachers may be next to go on strike for better wages.

Another worrying sign: As boomers age, they will need personal care aides, a job requiring numerous nuanced skills including empathy. They earn an average of $10.92 an hour.