Vacancy Chains: How One Resignation Can Trigger Five Career Moves

On Monday, the head of platform engineering resigns. By Friday, a staff engineer has been asked to step up. Her tech-lead role is offered to a senior engineer from the payments team. Payments now needs a senior engineer, so a mid-level engineer is promoted. His old role gets backfilled by an internal transfer from QA automation. And QA — finally — opens an external requisition for a junior engineer. One resignation. Five career moves. Four teams disrupted. One external hire, three months later. Your headcount report shows exactly one vacancy.

The idea that changed mobility research

In 1970, Harvard sociologist Harrison White published Chains of Opportunity, a study of clergy moves in three American Protestant churches. His insight was to follow the vacancy rather than the person. When a job opens and is filled from inside, the job the mover left is now vacant; when that is filled from inside, another opens. The vacancy travels through the system until it is filled from outside or the job is eliminated.

The implication was radical for its time: much career mobility is created by the structure of opportunities, not only by the talent or ambition of individuals. People get promoted partly because a chain reached them. Ivan Chase's review in the Annual Review of Sociology (1991) showed the same logic across settings as varied as housing markets and animal shelters, and Stewman and Konda (1983) modelled how the shape of an organisation's hierarchy determines promotion chances at each level.

Why HR keeps underestimating vacancies

Most workforce plans count vacancies at the point of exit. But the real workload of a vacancy chain is multiplied: several job transitions, several onboarding curves, several managers adjusting to new direct reports, several knowledge handovers. A chain of length five does not create one ramp-up period; it creates five overlapping ones.

Chains are also your best development engine

Vacancy chains are not just a disruption to manage. They are the main way organisations create promotions. Bidwell's research on internal mobility found internal promotees tend to perform better in their early years than more expensive external hires. Every time a senior role is filled externally, the chain is cut at the top and every potential internal move below it disappears. That is a quiet choice with large consequences for retention: a single external senior hire can end several people's next step.

How to manage a vacancy chain

A Nepal and remote-team angle

For companies building distributed teams — including engineering centres in Kathmandu serving global clients — vacancy chains often cross borders. A senior exit in London may be filled by a lead in Kathmandu, opening a role there. If local compensation bands, employment contracts, and promotion paths are not ready, the chain stalls in the middle and the organisation ends up with a gap nobody planned for.

Limits and caveats

• White's original data came from church clergy; later research confirmed the logic in many settings, but chain lengths vary widely by industry and structure.
• Flat organisations produce shorter chains because there are fewer levels to move through.
• Chains are not always good: promoting people into roles they are not ready for just to fill a gap creates new problems.

The research behind the chain

Sociologist Harrison White introduced the idea in Chains of Opportunity (1970). Studying clergy in American churches, he showed that when a job opens, the person who fills it usually leaves a job behind, which opens another, and so on until someone enters from outside or the post is closed. White found that the vacancy, not the person, is the thing that moves through the system. Mobility is driven by openings as much as by ambition.

Ivan Chase (1991) reviewed vacancy-chain research across settings as varied as housing markets and hermit crabs swapping shells. The pattern holds: one new opening at the top of a system can create several moves below it. Stewman and Konda (1983) applied the logic to organisational careers and showed that promotion chances depend heavily on the shape of the hierarchy and how often positions open above you — not only on individual merit.

Mapping a real chain

Four months later, five people are in new roles, three teams have changed, and at least four managers have run a selection process. If HR treated this as 'one resignation', it measured the event, not the impact.

What chains cost and create

Using chains in workforce planning

1. Measure historical chain length: for the last 20 senior exits, count how many internal moves followed each one.
2. Tag chain-starting roles: senior roles that routinely trigger long chains need earlier succession planning.
3. Find chain-breakers: roles that always end in external hiring show where the internal pipeline is thin.
4. Model the calendar: if a chain usually takes four months to settle, a Q4 resignation affects Q1 delivery in several teams.
5. Decide the exit point deliberately: sometimes hiring externally at a higher level shortens the chain and reduces disruption.

When to shorten a chain — and when to lengthen it

Long chains are good for development and retention: more people move up. They are risky when several critical teams are already stretched. Short chains — hiring externally for the vacated role — protect stability but can signal to employees that growth happens elsewhere. There is no right length, but there should be a deliberate choice, made by someone who can see the whole chain.

• Every senior resignation triggers a quick chain forecast.
• Backfill budgets cover the moves the chain will create.
• HR can report the average chain length for key role families.
• Managers down the chain are told early that a move may come.

Worked case: one director leaves, five people move

A product director resigns. The company promotes a senior product manager into the role. Her old role is filled by a product manager from another team. That team backfills by promoting an associate. The associate role is finally filled by an external graduate hire. One resignation has produced four internal moves and one external hire.

Each move comes with a learning curve. If every person needs about three months to settle, the organisation is running with several people in new roles at the same time, all inside one product area. Planning that treats the director's resignation as 'one vacancy' will badly underestimate the disruption — and the opportunity.

Questions to ask before you approve the first move

1. How long is the likely chain? Map at least three steps ahead.
2. Where does the chain end — in an external hire, a role you remove, or a gap?
3. Which of the moves are into roles that are hard to learn quickly?
4. Can any step be staggered so that not everyone is new at once?
5. Who is handing over knowledge, to whom, and by when?

Turning chains into a development tool

Vacancy chains are not only a risk to manage. They are the main way most people get promoted. A company that hires externally at the top of every chain shortens it, which means fewer internal moves and less development further down. A company that always promotes from within lengthens chains, which creates more growth but also more simultaneous learning. Neither is right in every case. The point is to choose on purpose.

What each role can do

• HR business partners: draw the chain on paper for every senior resignation and share it with the hiring leader.
• Finance: budget for overlap and onboarding time across the whole chain, not only the first hire.
• Managers: prepare 'ready now' and 'ready in a year' names for every key role so chains move quickly.
• Recruiters: start the end-of-chain external search at the same time as the first internal move.

Common mistakes

• Counting time-to-fill only for the first vacancy and ignoring the rest of the chain.
• Letting three moves start in the same week in the same team.
• Forgetting that the person at the bottom of the chain often gets the least onboarding.