Expert Answers: April 2021
This month’s question
Did W. Edwards Deming invent the plan-do-check-act (PDCA) cycle?
No, Deming did not invent or originate PDCA; it emerged in Japan. Deming’s earlier teaching in Japan may have influenced PDCA, but he never fully embraced it. He later published the plan-do-study-act (PDSA) cycle and credited Walter A. Shewhart.
Attributing PDCA to Deming is a common misconception. An informal poll of LinkedIn users, conducted in mid-2020, found that 72% of respondents thought it was Deming’s idea. Analysis of the poll data indicated the misunderstanding spans across continents, industries and job functions.
Some may find the distinction trivial, and it is fair to admit that understanding the origin of the PDCA cycle has little or no effect on the application of such concepts. Still, it is a point of heritage—heritage concerning important forebears of our field.
Deming’s work is a good place to seek clarity. In his 1986 canonical quality classic Out of the Crisis,1 there is a figure labeled “The Shewhart Cycle” (see Figure 1). It doesn’t yet carry the catchy PDCA title (nor the PDSA variation), but identifies a cycle of planning, doing, checking and acting, and credits a 1939 work by Shewhart for the idea.
THE SHEWHART CYCLE
To further connect the dots to the PDSA cycle, Deming’s 1994 book, The New Economics,2 will help. In the book, the Shewhart Cycle figure is updated to a now recognizable form, complete with letters P, D, S and A (see Online Figure 1). The new form carries the title “The Shewhart Cycle for Learning and Improvement; the PDSA Cycle.”
ONLINE FIGURE 1
THE SHEWHART CYCLE FOR LEARNING AND IMPROVEMENT
Given Deming’s evidence, it’s fair to credit Shewhart with the origin of PDSA, but it’s important to recognize that all continuous improvement cycles draw on fundamental concepts from much earlier. The underlying scientific method is found in Deming’s PDSA and the Japanese PDCA cycles. The hypothesis-experiment-evaluation process, written by Francis Bacon in 1620,3 is a common ancestor linking all continuous improvement cycles to the scientific method.
Debate persists on the differences between PDCA and PDSA, but the entwined lineage suggests the differences may be more trivial than the proper attribution of the terms’ origins. There are arguments for uniqueness between PDCA and PDSA, but the common theme of the scientific method persists. PDCA has prevailed, while Deming arguably has become the most recognizable name in quality.
Misattribution and misunderstanding of the improvement cycle is pervasive and not new. Deming addressed it so succinctly in a footnote in Out of the Crisis that it is reasonable to believe he was aware of the issue more than 35 years ago:
“I called it in Japan in 1950 and onward the Shewhart cycle. It went into immediate use in Japan under the name of the Deming cycle, and so it has been called there ever since.”4
This was Deming’s attempt to set the record straight, and we do the same.
- W. Edwards Deming, Out of the Crisis, MIT Press, 1986.
- W. Edwards Deming, The New Economics, MIT Press, 1994.
- Francis Bacon, Novum Organum, 1620.
- Deming, Out of the Crisis, see reference 1.
This response was written by W. Frazier Pruitt, senior engineer and quality assurance supervisor, Southco Inc., Rochester, NY, and S.M. Waqas Imam, management system consultant, Exoexcellence (SMC) Pvt. Lt , Karachi, Sindh, Pakistan.
Article originally published in Quality Progress April 2021
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