Despite a lot of recession fears, it doesn't seem like the Great Resignation will be slowing anytime soon. Another 4.3 million workers quit their jobs in May—and a new McKinsey report suggests that 40% of the workforce are still very unhappy with their jobs and looking for new opportunities. This is bad news for hiring managers.

“This isn’t just a passing trend, or a pandemic-related change to the labor market,” Bonnie Dowling, one of the report’s authors, told CNBC. “There’s been a fundamental shift in workers’ mentality, and their willingness to prioritize other things in their life beyond whatever job they hold.”

But it isn’t just the desire for remote work or higher pay that’s driving workers to look for new roles. In the McKinsey report, which surveyed more than 12,000 individuals in the U.S., Canada, U.K., Australia, India, and Singapore, 41% said that the lack of opportunity for upward mobility was the number-one reason why they left.

Workers are “increasingly moving to companies that give them both fair terms today and the chance to add experience that will better their prospects in the future,” Bill Schaninger, leader of McKinsey’s people and operational performance practice, and Anu Madgavkar, partner at the McKinsey Global Institute, wrote in Fortune last month. “The way for employers to attract a flow of new talent and stem the drain of attrition is to deliver on both fronts.”

The other reasons workers gave for leaving a job were uninspiring or uncaring leaders, followed by lack of meaningful work, unsustainable work expectations, lack of support, and lack of flexibility.

“[P]lenty of employees say that they see no room for professional or personal growth, believe that there is better money to be made elsewhere, and think that leaders don’t care enough about them—tried-and-true reasons for disgruntlement, to be sure, but ones that are now being acted upon broadly,” the report authors wrote.

McKinsey’s findings align with other research that suggests that workers—especially the younger generations—are looking for jobs that offer career advancement above many other popular perks, like flexible hours or hybrid work.

In a recent LinkedIn survey, 40% of Gen Z workers said they’d be willing to accept a 5% pay cut for a job offering significant career growth opportunities.

“People want to grow; they want to grow quickly,” Oliver Pour, a 2022 college graduate, told Fortune in May. “The mentorship aspect is extremely important, being able to connect with the manager or director on a more personal level.”

Promoting continuous growth and development as a cornerstone of company culture is the best bet for keeping people around, McKinsey's Dowling told Fortune’s Sheryl Estrada in an interview for CFO Daily. “Compensation is important, but if your leaders are not inspiring and they aren’t engaging and developing employees, compensation won’t be enough."

This story was originally featured on Fortune.com