Employers tend to keep head counts high for low-level hourly jobs so that they have a large pool of workers who can be scheduled for short shifts at times of peak demand. Technologies like computerized scheduling systems and forecasting tools make it possible to predict and monitor sales and calibrate work schedules not just by the day but by the hour. Employees are called in or sent home as needed. For each of these jobs there are often three workers available.

Although over- and underemployment create different challenges for workers, the trade-offs are strikingly similar. “Availability” is now a major form of human capital, in both high-powered salaried positions and low-level hourly jobs. Low-wage workers need to be available at all hours or risk not having work. Professionals are expected to remain electronically tethered to their jobs day and night or risk forgoing coveted opportunities. Both groups of workers lose earnings if they interrupt their careers to care for family members — as women at all points on the socioeconomic spectrum are more likely to do than their male counterparts.

Improving workplace norms may be essential to achieving gender equality, as the Princeton professor Anne-Marie Slaughter suggested in her recent essay in The Atlantic, but it will not change the incentives that foster over-employment at the top of the labor market and underemployment at the bottom.

To do that, the government must reform the Fair Labor Standards Act. Enacted in 1938 — decades before women’s labor force participation became the norm — the law established a minimum hourly wage but did not guarantee minimum weekly hours for any job (though unions may bargain for minimum hours). This reform would encourage employers to make full use of their hourly employees instead of overhiring, at low cost, a pool of on-demand shift workers.

The law also did not mandate that salaried workers get overtime pay. Requiring overtime pay for professionals would encourage employers to minimize unnecessary face time and to hire assistants to reduce the demands on professionals.

Such sweeping changes to labor laws might be politically impossible today, in an environment that is friendly to corporations and indifferent, if not hostile, to workers. But they are essential. They would press employers to hire one worker for one job, easing work-life challenges at both the top and the bottom of the labor market. That would create more entry-level professional positions for college graduates and better-paying jobs to lift low-income families into the middle class. It’s what women want and what our economy needs.