The 5 Shrinkage Calculation Mistakes Destroying Your Staffing Accuracy

Shrinkage is the single most miscalculated metric in WFM. The industry average hovers around 30-35%, but most teams are either massively over-counting (including items that should be handled separately) or dangerously under-counting (missing categories entirely). Both errors cascade through your staffing model and destroy forecast accuracy.

Mistake #1: Double-counting breaks. If your ACD already excludes break time from available minutes, and you’re also applying a shrinkage factor that includes breaks, you’ve just subtracted breaks twice. This alone can inflate your FTE requirement by 8-12%. Mistake #2: Using a single annual shrinkage rate instead of seasonal or monthly rates. Shrinkage in January (flu season + post-holiday turnover) is fundamentally different from July (vacation peaks). A flat 33% rate means you’re overstaffed half the year and understaffed the other half.

Mistake #3: Ignoring the difference between planned and unplanned shrinkage for scheduling purposes. Mistake #4: Not separating internal shrinkage (coaching, team meetings) from external shrinkage (sick, personal) — because internal shrinkage is controllable and should be managed differently. Mistake #5: Applying shrinkage after Erlang C instead of before, which understates the true agent requirement. The fix for each is straightforward once you understand the math.

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