Flight Risk Score
Also known as Attrition Risk Score, Turnover Risk Model
A flight risk score is a modelled probability that a given employee will voluntarily leave within a defined horizon, usually the next six or twelve months. Unlike turnover rate, which reports what already happened, it is a forward-looking estimate built from tenure, engagement, compensation position, manager history and internal movement data.
Formula
Typically a logistic regression or gradient-boosted model: P(leave within horizon) = f(tenure, time in role, compa-ratio, engagement trend, manager change, promotion recency, commute, peer attrition)There is no universal formula — the value is in a model fitted to your own historical exits. A model trained on someone else's data will not transfer, because the drivers differ by organisation.
Worked example
- Scenario
- A model trained on three years of exits scores a 200-person engineering group, flagging the top decile as elevated risk.
- Calculation
- 20 employees scored above the 0.35 probability threshold; of those, historical precision suggests roughly half would leave within 12 months absent intervention
- Result
- A shortlist of 20 for manager conversations, rather than a 200-person retention campaign
What good looks like
Judge the model on precision within the top risk decile rather than on overall accuracy. Because base attrition rates are low, a model that predicts 'nobody leaves' will score highly on accuracy and be worthless. Useful models typically identify a top decile containing several times the base rate of actual departures.
Why flight risk score matters
Retention budgets and manager attention are finite. A ranked risk list directs both at the people most likely to leave and most costly to lose, which is a materially better use of effort than a company-wide intervention. It converts retention from a reactive exercise into a planned one.
How to improve it
- 1Train on your own exit history — at least two years, ideally three — rather than importing assumptions about drivers.
- 2Weight the output by role criticality and replacement cost so the list reflects impact, not just probability.
- 3Give managers the drivers behind each score, not just the score. A number with no explanation produces no action.
- 4Re-fit periodically. Drivers shift with the labour market, and a model trained on a hiring boom misreads a downturn.
- 5Measure whether flagged employees who received intervention stayed at a higher rate than flagged employees who did not.
Common mistakes
- Using accuracy as the evaluation metric on an imbalanced outcome, which rewards a model that predicts no attrition at all.
- Including protected characteristics as features, directly or via close proxies — a legal and ethical problem as much as a modelling one.
- Exposing individual scores without governance, which damages trust far faster than the model creates value.
- Treating the score as a verdict rather than a prompt for a conversation.
Frequently asked questions
Is it ethical to score employees on flight risk?
It can be, with governance. The defensible version uses the score to trigger a supportive conversation and excludes protected characteristics and their proxies. The indefensible version uses it in promotion, pay or assignment decisions, which converts a retention tool into discrimination.
How much data do I need to build a flight risk model?
Realistically two to three years of exit history and a few hundred separations. Below that, a well-designed rule-based risk flag — tenure band, time since last promotion, compa-ratio, engagement trend — will outperform an under-trained model.
Related metrics
Regretted attrition rate is the share of departures the organisation would have preferred to prevent — typically strong performers, people in critical roles, and those with scarce skills. It is the retention metric that correlates most directly with business impact, because it strips out the exits that were neutral or beneficial.
Voluntary Turnover RateVoluntary turnover rate is the percentage of employees who choose to leave — resignations and retirements — as a share of average headcount. Isolating it from involuntary exits is what turns a turnover number into a retention signal, because only voluntary departures reflect decisions your organisation could have influenced.
Employee Engagement ScoreAn employee engagement score is a composite index built from several survey items covering commitment, discretionary effort and intent to stay. Unlike eNPS it is designed to be diagnostic, so the sub-scores that make it up matter as much as the headline figure.
Compa-RatioCompa-ratio compares an employee's actual pay against the midpoint of their salary band, expressed as a decimal or percentage. A ratio of 1.0 means the person is paid exactly at midpoint; below 1.0 means below midpoint, above means beyond it.
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