Researchers at the University of Chicago and the University of Michigan published a case study last week. The data was gathered from People Data Labs to understand the impact forced returns to offices had on employee tenure and workers' movement between companies.

The number crunchers found was a strong correlation between the departures of senior-level employees and the implementation of a mandate, suggesting that these policies "hurt the tenure and seniority of their respective workforce."

High-ranking employees stayed several months less than they might have without the mandate, the research suggests -- and in many cases, they went to work for direct competitors.

At Microsoft, the researchers found that the share of senior employees as a portion of the company's overall workforce declined more than five percentage points after the return-to-office mandate took effect.

At Apple, the decline was four percentage points, while at SpaceX -- the only company of the three to require workers to be fully in-person -- the share of senior employees dropped 15 percentage points.

One of the study’s authors, Austin Wright, said: "We find experienced employees impacted by these policies at major tech companies seek work elsewhere, taking some of the most valuable human capital investments and tools of productivity with them."

"Business leaders should weigh employee preferences and market opportunities carefully when deciding when, or if, they mandate a return to the office."

While the corporate culture and return-to-office policies differ "markedly" between the three companies, the similar effects of the RTO mandates suggest that "common underlying dynamics drive the effects," wrote the study's authors.

"Our findings suggest that RTO mandates cost the company more than previously thought," said David Van Dijcke, a researcher at the University of Michigan who worked on the study. "These attrition rates aren't just something that can be managed away."

Robert Ployhart, a professor of business administration and management at the University of South Carolina, said executives haven't provided much evidence that RTO mandates benefit their workforces.

"The people sitting at the apex may not like the way they feel the organization is being run, but if they're not bringing data to that point of view, it's really hard to argue why people should be coming back to the workplace more frequently," Ployhart said.

Senior employees, he said, are "the caretakers of a company's culture," and having to replace them can negatively affect team morale and productivity. "By driving those employees away, they've enhanced and sped up the very thing they were trying to stop," Ployhart said.