WIP and flow¶
There is a counter-intuitive result at the heart of operations theory:
Doing fewer things at the same time gets more things done.
This sounds wrong. If I work on 5 things at once, surely I make progress on 5 things? In practice, no. Each thing slows because context-switching costs are real and queueing time dominates. The fix is to limit work in progress (WIP).
Where it comes from¶
Taiichi Ohno developed the Toyota Production System in the 1950s (Ohno, 1988). One of his core insights: smoothing flow matters more than maximizing utilization. A factory where every machine runs at 100% has queues building everywhere; a factory where machines run at 80% with WIP limits ships parts faster.
David Anderson translated this to knowledge work in Kanban (Anderson, 2010). Jim Benson and Tonianne Barry scaled it down to personal use in Personal Kanban (Benson & Barry, 2011).
Little's Law¶
The math behind it is one line, called Little's Law (Little, 1961):
Average time in system = Work in progress ÷ Throughput
If you have 10 tasks open and you finish 2 per week, the average task sits open for 5 weeks. If you cut WIP to 4, the same throughput now means tasks finish in 2 weeks. Same work done. Half the lead time.
This is why pairing a Kanban board with explicit WIP limits is so powerful. The visible column tells you when you're overcommitted; the limit makes you stop starting new work and start finishing it.
How to set a WIP limit¶
Rules of thumb:
- Solo Operator: 3 in In Progress at any time. If you have 5, you have 0 — none of them are getting your real attention.
- Team Lead: 1.5× team size in In Progress across the team. A 4-person team should have no more than 6 things in progress at once.
Start with these numbers. Adjust based on what works.
How dooer enforces (or doesn't)¶
dooer does not currently enforce a hard WIP limit. It does two soft things:
- The 5-day workload gauge on Priority Matrix turns red when a day is overbooked (S-2.2). That's a daily WIP warning.
- The task board's column counts are visible at the top of each column. You can see when "In Progress" balloons.
The discipline is on you. Make a rule. Enforce it manually for 4 weeks. You will notice the difference.
The "stop starting, start finishing" mantra¶
The phrase came out of the Kanban community around 2010. It captures the WIP-limit discipline in 4 words. When you're tempted to start a new task, ask: which open task could I finish in the time it would take me to start this one? Almost always the answer is "one of them."
Where to read more¶
- Anderson, D. (2010). Kanban: Successful Evolutionary Change for Your Technology Business. Blue Hole Press.
- Benson, J. & Barry, T. (2011). Personal Kanban: Mapping Work, Navigating Life. Modus Cooperandi.
- Reinertsen, D. (2009). The Principles of Product Development Flow. Celeritas. A deep dive into the queueing-theory math.