TPS Benchmarking

Things They Say at Toyota: Ask “Why?” Five Times

By Jon Miller Published on October 19th, 2006

One of the ways to judge whether a company is succeeding in their journey towards being an organization that embraces continuous improvement based on the Toyota Production System model is how often people ask “why?” as part of the daily management and problem solving dialogue.
The five why process is excellent habit for two reasons. First, the traditional organization tends to ask “who?” five times rather than “why?”. Who did this? Who is to blame? Who is responsible for fixing this? Etc. This behavior results in problems being covered up, which only adds to the problem since they don’t get fixed. It’s a vicious cycle. Avoid this by asking “why?” five times.
Second, the five why process helps people get to the true root cause of a problem by questioning beyond the obvious answer to the first “why?” This is important because many times the first or even second answers to the “why?” question can be a commonly held belief or assumption that is incorrect. These are known as “facts” to the people who hold them and “myths” to people looking in from the outside.
As far as I know there’s nothing magical about the number five in ask “why?” five times. So what do you do if you can’t find the root cause after five, six seven or eight “why?” questions? When I was interpreting for Japanese sensei the answer was often “Think for yourself! You haven’t searched hard enough!” At the time I thought this was a convenient dodge, but now I realize that there is a lot of truth to the idea that “If you haven’t found it, you haven’t searched hard enough.”
Another way I think of this is “Failure is stopping before you succeed.”
There’s a five why story of a client of ours who had a quality problem. One piece flow could not be achieved, they said, because machine down times were very high. Why? There were too many rush orders to make parts that were damaged at the downstream processes. Why were there so many damaged parts? Parts were being damaged during transportation when they hit other parts. Why did they hit other parts? They were stacked high on a cart that was heavy, hard to move and the material handler could not see where he was pushing the cart. Why were the parts stacked so high? The production lot sizes were large because the machine had a high amount of down time. Why? Wait a minute…
At this point the people I was asking realized the ridiculousness of their situation (the large batch size was causing the defects, which was causing the large batch size) and soon we were flowing one piece at a time. They also saw the power of asking “why?” again and again until you succeed in finding a solution to a problem.
What’s your favorite five why story?

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