There are no simple answers.

When it comes to women over 50, one theory that makes sense to Mr. Monge-Naranjo is that those who dropped out of the labor force to take care of children when they were younger can’t easily get back in. “They did not see that the labor market was going to be so tough and it’s taking quite some time to go back to normal,” he said.

That has been Lynn Colafrancesco’s experience. Once a vice president at a reinsurance company, Ms. Colafrancesco, now 59 and divorced, started determinedly looking for a full-time job three years ago. As soon as she mentioned that she had taken off time to care for two children, she could see in the interviewer’s face that she had been summarily dismissed.

“Now I don’t even mention about my kids,” Ms. Colafrancesco said. “They don’t want to hear that.” To make ends meet, she works as a substitute teacher a couple of days a week and rents out rooms in her house in Fairfield, Conn.

Certainly older workers — male and female — must contend with age discrimination.

“I have been told in interviews that they want somebody younger,” said Karen Lamkin, a lawyer with 25 years of experience who lives outside Boston and has been out of work for three years. “It does not matter that I would be satisfied with the salary for a junior position.”

A shrinking network of professional contacts, and possibly fewer cutting-edge skills, can also hamper older workers in the job hunt, said Connie Wanberg, a professor at the Carlson School of Management at the University of Minnesota. In a world where networking is done more and more online, they may be less adept at the latest techniques. Older workers can also be pickier, Ms. Wanberg said — more reluctant to relocate away from family, for example, or to do certain kinds of jobs.

The question is whether these factors operate even more powerfully for women than for men, Ms. Wanberg said. Women, who are much more likely to be burdened with caregiving responsibilities, even as they age, may require more flexibility in their schedules, for example.