The Birthday Paradox of Process

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The Birthday Paradox of Process

Podcast Episode · Process Debt · 09/05/2025 · 19m

If you’ve ever heard of the birthday paradox, you know the trick: you only need 23 people in a room for there to be a coin-flip chance two share a birthday. Our intuition expects a much bigger number. Reality says otherwise.

Work is full of similar traps. We assume complex problems demand bigger meetings, more stakeholders, one more invite “just in case.” Then we wonder why decisions slow to a crawl.

Here’s the kicker with birthdays: the probability spikes because every new person creates new possible pairs. Add one person, you add a lot of possible matches. Meetings behave the same way. Each extra attendee multiplies communication paths, opinions, and alignment checks. At ~40 people, the birthday match is above 90%. In meetings, the “match” you get is confusion.

Lately I’ve noticed how effortless it is to swell a calendar. In the pre-Zoom world, you had to coordinate bodies and rooms. Now you click “Add.” We invite because it’s polite, or because we’re not perfectly clear on the problem, or because we’re low-key anxious and want company. None of those are great reasons to tax a decision with more channels.

Early in my career, we used to talk about skunkworks teams: five or six people, max. Clear purpose. Tight feedback. Known decision rights. That wasn’t nostalgia; it was operational wisdom. Fewer edges to the shape means fewer places to snag.

The turn: complexity doesn’t demand more bodies — it demands more clarity. Like the birthday paradox, our intuition says “more” will help us find a match faster. In practice, “more” increases the odds of a mismatch: misread goals, muddled roles, and meetings that become status theater instead of decision engines.

So what do we do instead?

1. Define the meeting by its verb. Decide. Diagnose. Design. Debrief. Different verbs require different voices. A “Decide” meeting needs the smallest set of accountable roles and the actual decision maker. A “Diagnose” session might cast a slightly wider net — but with clear timeboxes and a recorder, not a chorus.

2. Assign roles before you hit send. Voters, advisors, observers. It’s okay to invite people to listen live and not opine. That’s transparent, not rude. If someone’s presence is for awareness, say so. If someone can block the outcome, they either join as a voter or they bless the decision in writing beforehand.

3. Put the constraint on the table. Budget, timeline, headcount, risk tolerance — name the real boundaries up front. More experts won’t save you from hidden constraints; they’ll just find more ways to collide with them. Complexity without visible constraints invites wheel-spinning.

4. Move decision rights closer to the work. Toyota’s lesson endures: the people doing the work often hold the sharpest information. If your meeting consistently excludes them — or includes everyone except them — you’re building process debt by design.

5. Trade breadth for cadence. Need wider awareness? Don’t cram it into the decision forum. Send a crisp written update. Hold a short debrief later. Record the meeting and timestamp the decision. Decouple deciding from socializing.

A simple mental model helps me keep my calendar honest: every additional attendee adds a channel tax. Are they worth the tax for this verb, under these constraints, with this decision maker in the room? If yes, invite with a role. If no, share the notes.

We don’t need to outlaw big meetings. We need to stop believing they’re our default. The math — and the outcomes — say otherwise.

Process Debt Truth: Every extra seat you add to a decision adds a new place for clarity to leak.