witkeepDiscover Witkeep ↗What HR accounts for
Replacing an employee costs between 100% and 250% of their annual salary, depending on seniority (Gallup, 2024). This includes recruitment, onboarding and the four to six months needed for the successor to reach the same productivity level (Bloomfire, 2025). For a manager earning €80,000 a year, that means €80,000 to €200,000 per departure. This is the visible cost — and the point where most organisations stop measuring.
The first hidden cost: duplication
When an expert leaves without documenting their methods, successors repeat work already done. This is not theoretical: 65% of employees recreate work every week that has already been done elsewhere in their organisation — without knowing it (Bloomfire, 2025). Without a system for retaining knowledge, employees spend an average of 8.5 hours a week searching for information that already exists, compared with 4.6 hours in organisations with a knowledge management programme.
saved per employee per week through structured knowledge management. Across 1,000 employees, this is equivalent to freeing up 98 full-time roles — without hiring. (Bloomfire, 2025)
This lost time is never counted as a cost of turnover. It should be. In a 200-person organisation with 15% turnover, it is a productivity drain that returns every year.
The second hidden cost: competitive advantage transferred
This is the hardest cost to quantify — and often the most expensive. 42% of an organisation’s institutional knowledge exists only in people’s heads (Panopto Workplace Knowledge Report): undocumented, non-transferable and unmeasured. When these people leave, that knowledge does not disappear. It goes with them.
In many cases, it goes straight to a competitor. The growth specialist who takes their automations, email sequences and refined AI prompts. The sales director who takes their network and qualification methods. The consultant who rebuilds at a competitor the system developed with your resources. What was your competitive advantage becomes theirs — built at your expense. See Marc’s story for a concrete example.
How AI changes the equation
Since 2023, a third cost has entered the calculation. 68% of employees use personal AI accounts to access tools such as ChatGPT or Claude, and 57% of those use sensitive data — meaning 39% of all employees expose critical information outside any oversight (Menlo Security, 2025).
Prompts refined over months, AI workflows built through repeated iteration, organisational context embedded in conversation histories — all of this lives in individual accounts. When someone leaves, they take not only what they know but also the systems they built with your resources. This is knowledge drain applied to AI.
lost on average each year by companies because of poor data and knowledge management, according to Gartner. (Source: HBR Sponsored, 2025)
What this means for leaders
The real cost of a departure is not an operational inevitability. It reflects an architectural choice. Organisations that handle departures well treat internal knowledge as a collective asset: documented, centralised and portable. Not as individual property that each employee takes away.
The question is not “how do we retain talent?” It is “how do we ensure the organisation knows what each individual knows — and retains that knowledge when they leave?” To explore the related challenges, see the six challenges or the FAQ.