The Real Cost of Wrong Shrinkage Assumptions — What 15-20% Is Costing Your Call Centre Every Day

I spent 30 years inside Canadian telecom call centres — Rogers, Telus, Bell. And in every single workforce planning review I sat in, the shrinkage assumption was the same: 15 to 20 percent.

Not because anyone had calculated it. Not because it reflected reality. Because someone had written it in a textbook once, and it had never been challenged since.

That number is costing your call centre millions. Let me show you exactly how.

What Shrinkage Actually Is

Shrinkage is every hour a scheduled agent is not handling calls. It includes:

Planned shrinkage — paid breaks, team meetings, training sessions, one-on-ones, coaching, performance reviews.

Unplanned shrinkage — sick days, lateness, no-shows, bereavement leave, personal days.

Auxiliary shrinkage — system outages, after-call work overruns, off-phone project time.

When you add all three together for a real call centre — not a textbook one — the number is rarely 15 to 20 percent. In telecom environments I worked in, total blended shrinkage typically ran between 24 and 32 percent, depending on the centre, the season and the workforce profile.

That gap between 18 percent and 28 percent on a 500-seat call centre is roughly 50 agents understaffed on any given day.

Fifty agents. Every day.

What That Gap Actually Costs

Here is what happens when you underestimate shrinkage by 10 percentage points on a 500-seat inbound centre:

SLA breaches. Your service level drops. Calls abandon. Customers wait. The metric your operations team reports to the board is already wrong before the day starts.

Customer churn. In telecom, a customer who waits too long and abandons has a measurably higher probability of cancelling within the next 90 days. One understaffed shift does not cause churn. Three months of understaffed shifts does.

Excess overtime. Your supervisors react to the gap by pulling people into overtime. That overtime was not in the budget. It never is, because the budget was built on a shrinkage number that was never real.

Revenue leakage. If your call centre handles inbound sales or upsell, every abandoned call is revenue that walked out the door. Not a metric. Real money.

Staff burnout. The agents who do show up carry the load for the ones who did not. Engagement scores drop. Attrition rises. Which increases unplanned shrinkage. Which increases the gap. Which increases overtime. The cycle accelerates.

I have seen this play out at scale inside billion-dollar corporations. The root cause, every time, was a shrinkage number that was guessed rather than calculated.

Why the Textbook Number Persists

The 15 to 20 percent assumption persists because it is easy. It requires no data. It requires no analysis. It goes into the Erlang calculator, produces a headcount number, and nobody questions it until the SLA report comes back red.

By then, the damage is done. The quarter is over. The overtime has been paid. The customers have churned.

Most workforce management tools are built by people who have studied call centres. Not by people who have run them. The textbook assumption is comfortable for people who have never had to explain a $2 million overtime variance to a CFO.

I have had that conversation. Multiple times.

What the Right Approach Looks Like

Shrinkage should be calculated from your actual operational data — not assumed from a range. That means attendance records broken down by team, shift and tenure, training schedules by quarter, system downtime logs, after-call work actuals versus targets, and union contract provisions if applicable.

When you calculate shrinkage from real data, it stops being a single number. It becomes a dynamic input that changes by month, by team, by season — and your staffing model updates with it automatically.

That is what the Call Centre Workforce Planning Dashboard does. It calculates your exact shrinkage from your data, feeds it directly into your WFM staffing model, hiring plan, training schedule and capacity model — and updates everything downstream the moment any input changes. It also supports 5 to 10-year medium and long-term planning horizons.

The Board Narrative Your CFO Actually Wants

When you need to take the workforce plan to the board, the dashboard generates a board-ready ARCTIC framework narrative in one click. Not a slide deck you spend three days building. A structured, professional narrative that explains the situation, the root cause, the financial impact, the recommended action and the expected outcome — in 30 seconds.

Start With Your Own Data

Every call centre is different. The right shrinkage number for your centre is in your data right now. You just need the right tool to calculate it.

Try the Call Centre Workforce Planning Dashboard free for 14 days — no booking required.

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