The risk in hiring a team together isn't that they leave. It's that your team does.

You just hired a new operations manager, and in the second interview she asked if she could bring her old scheduler and her best technician with her from her last job. You said yes almost without thinking about it. It meant three fewer job postings, three fewer weeks of someone fumbling around your systems, and a manager who wouldn't spend her first quarter building trust from nothing. It felt like a discount.

A study published August 15 in Personnel Psychology — a peer-reviewed journal, not a vendor report — suggests you should think about that discount differently, because someone else in the building is paying for it.

The paper, "Newcomer and Incumbent Exit After Comobility Hiring Events," is by Luciana Zheng Manroop (University of Cincinnati and Penn State), Rhett Andrew Brymer (University of Cincinnati), and Aaron D. Hill (University of Florida). They study "comobility" — hiring events where two or more people move to a new employer together, bringing an existing working relationship with them. Rather than survey people about their feelings, the authors pulled real personnel records: eighteen years of U.S. college football coaching staffs and eighteen years of partner moves at the highest-revenue U.S. law firms, the Am Law 200 (both 2001–2018) — occupations where job changes and reporting lines are unusually well documented. They backed that with a smaller, exploratory survey and eight interviews with people who'd lived through a comobility hire, run to check whether their theorized mechanism — a sense of belonging, or "embeddedness" — held up in people's own words. The interviews are illustrative, not a representative sample, and the authors say so themselves.

The finding: bringing people along is a genuinely good move for the people who move. Coaches who arrived with at least one colleague were 22.7% less likely to leave within a year than coaches who arrived alone. Lawyers who moved in a group were 17.3% less likely to exit than solo movers. That part is intuitive — you land somewhere new with an ally already in the room.

The part that isn't intuitive is what happens to the people already there. On coaching staffs that absorbed a comobility group, incumbents were 1.8 times more likely to exit within a year. At law firms, incumbent exits in a branch rose 33.4% after a comobility group arrived. It gets worse specifically when the incoming group has a designated leader — a new boss who picked her own people to bring. With a leader present, incumbents' one-year exit likelihood rose from 36% to 49%, while the comovers' own exit risk dropped from 33% to 18%. The same leader who anchors the newcomers is the one destabilizing everyone else.

The authors can't observe intent directly — this is archival data, not a survey of why people quit — so they used instrumental variables to rule out the more obvious alternative explanations (pay, performance, cost of living) before trusting the pattern. What the interviews add is texture on the mechanism:

"We brought in [two new hires] who came in together from [another organization]. It upset the apple cart a bit. They come in thinking they've got all these answers because it worked for them at [their prior employer]. It took some time to get on the same page."

An incumbent interviewee, quoted in Manroop, Brymer & Hill, "Newcomer and Incumbent Exit After Comobility Hiring Events," Personnel Psychology, 2026

Here's why this lands differently for you than for the head of HR at a five-thousand-person company. At that scale, a rough integration after a package hire is noise — a few resignations get absorbed into a workforce nobody can fully see anyway. At a company where forty or eighty people make up the whole roster, losing your ops lead and your best account manager in the same stretch isn't noise. It's a meaningful share of your institutional memory walking out inside a year, right when you thought you'd gotten a great deal on a new manager.

The part the research doesn't say, but that I'll say plainly: this isn't about the new people being disloyal or the incumbents being fragile. It's arithmetic. A manager who arrives with her own trusted second doesn't need your incumbent's judgment the way she would if she'd arrived alone. She already has a backup opinion in the room. That changes whose read on a problem gets weighed first, and it changes before anyone says a word about it out loud. People don't need to be told they've been demoted in influence. They do the math themselves, then start looking.

The authors' own read, worth taking seriously since they didn't have to say it: coaching staffs and law firm partnerships carry "executive duties similar to CEOs and top management team members," so they argue the pattern likely generalizes to executive hiring and succession more broadly — not just to sports and law.

One thing to do this week: if you're finalizing an offer that comes with "and can I bring one or two people," don't let the incumbents in that person's orbit find out where they stand by watching the org chart shift. Before day one, tell them directly what's changing, what isn't, and where their judgment still carries weight. It costs you twenty minutes. The alternative costs you the person you didn't mean to lose.

If hiring and succession decisions like this one keep landing on your desk without anyone helping you think them through, the Leadership Profile is built for exactly that seat.