The History of PDSA, PDCA, and Dr. Deming

PDCA, or “Plan Do Check Act”, is perhaps one of the most well-known concepts in lean and continuous improvement. Not the most understood, but well known about. Anything this ubiquitous and broad is with understanding its historical use and origins. I love diving into histories like this; read economics and I want to go back and read Adam Smith’s Wealth of Nations, or exploring the history of math through Euclid. When it comes to PDCA, knowing the name Dr. Deming isn’t enough. 

I was saddened to learn about the passing of Ron Moen last year, as we had lost far too many good people in the last year. I met Ron a very long time ago, although we had not kept in touch. He was a Deming Institute trustee and was Dr. Deming’s liaison to Pontiac in the 1980s. This connects to me as my former partner Denny Pawley was running the Pontiac Fiero plant during the time of Dr. Deming’s visits. 

Few were in a better position to understand the history of Dr. Deming’s thinking, and of PDCA, than Ron was. In honor of his work, I went back and reread his article Foundation and History of the PDSA Cycle. You can read it for yourself, but here are a couple of takeaways. 

1. Dr. Deming wasn’t about PDCA but PDSA

Ron points out that Dr. Deming told his audiences that PDCA wasn’t right…”he warned audiences that the plan, do, check, and act version is inaccurate because the English word “check” means “to hold back.” That’s obviously not the intent. PDCA came from Japanese executives recasting the Deming Wheel, as described by Imai and eventually refined by Dr. Ishikawa. 

Deming eventually talked about PDSA, although it is unclear about when he started using it. I talked about the subtle difference years ago in this video.

Deming apparently hated PDCA. Never a man to pull punches, in letters he said “…be sure to call it PDSA, not the corruption PDCA.” He also said in response to PDCA “What you propose is not the Deming Cycle. I don’t know the source of the cycle that you propose. How the PDCA ever came into existence I know not.” 

Is it time to toss out PDCA, and just use PDSA? “Study” is such a more learning-oriented word than “Check”. 

2. Less about steps, more about integration 

Perhaps the wheel wasn’t the best image to use for this learning and improvement philosophy. For anyone who has significant experiences in teaching and coaching PDSA, you start to realize that it is really a fractal, where you have multiple PDSAs embedded in a set of larger PDSAs embedded in a large PDSA. Then it starts to get confusing about which level of the PDSA chain you’re currently working on. 

The inherent problem, in my opinion, is that we are overly treating PDSA as a set of 4 steps that follow a sequence. Actions do have completion, but when you truly internalize PDSA you don’t turn off the other perspectives when you are operating in one of the “steps.” You don’t stay in Plan until complete and then move on to Do. You are always on. You are always trying to understand cause and effect, always adjusting, always observing, always learning. Are they truly steps, or are they 4 interrelated perspectives that we integrate into all that we do? 

I’m not going to propose a new image, but I do suggest a new view of PDSA as integration rather than steps can be quite useful. Maybe we should call PDSA a fractal. 

3. Going back to Deming and Shewhart isn’t the “origin story” 

In most management theories, there are always some of us that want to go back to the origin story. We don’t want to read about modern lean stuff, but instead Taiichi Ohno and Shingo’s original works, or Henry Ford and River Rouge before them. Dr. Deming is often considered one of the original management thinkers on which almost all continuous improvement is built. 

Forget for a moment that Deming was building on Shewhart, yet we almost only talk about Deming. We can go much further. Deming and Shewhart were quite literally building on scientific thinking. Moen’s article outlines there were many thought leaders of scientific thinking, going back to John Dewey, Francis Bacon, and Galileo that they built on. 

If we’re serious about this, shouldn’t we all read John Dewey and Francis Bacon? Or go back even further, as I did with The Map of Knowledge, and understand Euclid and Galen. Study the origins, and we’ll all get smarter about the path ahead.