One of common patterns of adopting Kanban is that teams start just with visualization and, for whatever reasons, resist applying Work In Progress limits at the very beginning. While, and let me stress it, resignation from introducing WIP limits means drawing most of improvement power out of the system I understand that many teams feel safe to start this way.
If you are in such point, or even a step earlier, when you’re just considering Kanban but haven’t yet started, and you are basically afraid of limits I have a challenge for you. Well, even if you use WIP I have the very same challenge.
First, think of limits you might want to have.
Second, measure how the tasks flow through your process. It’s enough to write down the date when you start working on a task and the date when you’re done with it – the difference would give you a cycle time.
Third, after some time, check how many tasks in progress you really had every day. In other words: check what your WIP was.
Odds are you will be surprised.
One of my teams followed the “let’s just start with visualization and we’ll see how it goes” path. We even discussed WIP limits but eventually they weren’t applied. It is a functional team of 4 that juggles tasks which are pretty often blocked by their “clients,” i.e. beyond team’s control. The process, besides backlog and done bucket, is very simple: there’s only one column – ongoing.
The discussion ended up with the idea of limit of 8, considering there are some rather longish tasks mixed with quite a few short but urgent tasks, e.g. “needs to be done today” sort, and of course there are frequent blockers. In other words rough limits two tasks per person should account for all the potential issues.
As I’ve mentioned, WIP limits weren’t initially set. Even the WIP limit of 8 looked too scary at that point. After a few months we came back to the discussion. Fortunately, this time we had hard data from a hundred days.
Guess what the worst WIP was.
Seven. Over the course of a hundred days there wasn’t a single case that the scary limit of 8 was reached, let alone violated. What more, there were only 5 days where limit was higher than 6. In other words setting the limit of 6 and keeping it would be no sweat. A challenge starts at 5, which sounds very reasonable for such team.
All of that considering that each and every blocked item was counted within the limit as at the moment the team doesn’t gather the data to show how long a task remains blocked.
The lesson I got was that we can and should challenge our WIP limits basing on historical data. How often we hit WIP limits. How often we violate them. If it appears that we have enough padding that we barely scratch the ceiling on rare occasions it is a time to discuss reducing WIP limits. After all, it might mean that we are pursuing 100% utilization, which is bad.
If WIP limits are barely and rarely painful, they aren’t working.