LONDON: Every now and then, a country has a nationwide debate that produces actual learning. It happened in the United Kingdom about two years after the vote for Brexit, when many people belatedly found out about the workings of the European single market.

I’ve spent much of this winter following the French debate about the right retirement age, as the government’s bill sought to raise the age from 62 to 64.

The argument has raged everywhere from the marches along my road in Paris to “up yours” gestures in parliament.

Surprising truths have emerged that apply far beyond France. I previously wrote that the French led the world in allowing people a first golden decade of retirement. My main conclusion now: That lower social classes should be allowed to retire about a decade before higher ones.

JOBS, NOT CAREERS

Broadly speaking, there are two kinds of workers: The low paid and the high. The high paid tend to study well into their twenties and then might spend years choosing a career. They have lots of autonomy at work, sometimes with an office and even a toilet to themselves.

They control their own schedules, ratchet up their salary and status over time and decompress during holidays by the pool. Some never want to retire. The high typically live into their eighties.

Then think of low-paid workers like cleaners, cashiers and construction workers. They often enter vocational training in adolescence and start work by 18. They have little autonomy: They u...