Is Lean the Same as TPS?

Leans Journey4


No, at least not to the discriminating eye, as shown in the above image (click on image to enlarge). That does not mean Lean is bad or that one cannot achieve some great things with Lean. But it is important to understand that Lean and TPS are not the same, and therefore the results that are possible can be different in several important ways. The above image shows key differences between TPS and Lean and how Lean has changed over the years. These changes have contributed to the confusion over what Lean is. While TPS is never static and continues to evolve, its fundamentals have remained the same.  

Professor Yasuhiro Monden studied Toyota’s production system in the early 1980s. As part of his research he had direct contact with Taiichi Ohno and his disciples, and communicated with them in Japanese. In his book, Toyota Production System: Practical Approach to Production Management (first edition, 1983, page 2), Monden characterizes TPS this way:

“…although cost-reduction is the system’s most important goal, it must achieve three other sub-goals in order to achieve its primary objective. They include:

1. Quantity control, which enables the system to adapt to daily and monthly fluctuations in demand in terms of quantities and variety;
2. Quality assurance, which assures that each process will supply only good units to subsequent processes;
3. Respect-for-humanity, which must be cultivated while the system utilizes the human resources to obtain its cost objectives.

It should be emphasized here that these three goals cannot exist independently or be achieved independently without influencing each other or the primary goal of cost reduction. It is a special feature of the Toyota production system that the primary goal cannot be achieved without realization of the subgoals and vice versa. All goals are outputs of the same system; with productivity as the ultimate purpose and guiding concept, the Toyota production system strives to realize each of the goals for which it has been designed.”

This is consistent with what I learned from Shingijutsu more than twenty years ago. It is also consistent with the team member handbook that Toyota created in 1984 for its joint venture with General Motors, called NUMMI.

In their influential 1990 book, The Machine that Changed the World: The Story of Lean Production, Womack, Jones, and Roos presented “lean production” as a term synonymous with TPS. The same was true for Krafcik’s 1988 paper, “Triumph of the Lean Production System.” Lean was therefore not separately defined. The lack of definition also led to a lot of confusion.

Today, Lean is generally regarded as a generic term for TPS, but is not synonymous. Is something presented as the same actually the same? If company A were to practice Lean and company B were to practice TPS, all other things being equal, would the outcomes be the same? No, they would not. The results from Lean may be good and beneficial, but they will not be the same as from TPS.

In their influential 1996 book Lean Thinking: Banish Waste and Create Wealth in Your Corporation, Womack and Jones used the term “lean thinking” to describe what they had learned in their research about the people who were creating Lean organizations. They defined “lean thinking” as consisting of the following five principles that guided people’s actions (pp. 10 and 16-26):

  1. Specify Value
  2. Identify the Value Stream
  3. Flow
  4. Pull
  5. Perfection

Subsequent definitions and characterizations can be found here. This is inconsistent with what I learned from Shingijutsu more than twenty years ago. Note that Mondens’ book described TPS as “management,” while Womack and Jones’ book described Lean as “wealth creation.”

The term “lean production” is an interpretation of the Toyota Production System that is much lower fidelity than TPS itself, encompassing major differences in mindset, objectives, methods, and outcomes. Lean, being a poor interpretation of TPS, led people astray for a very long time – especially with regards to the nexus between human relations (social interaction) and continuous improvement. Unfortunately, senior managers’ quest for wealth creation using Lean did much harm to workers (e.g. lack of trust, layoffs, benefits accrue to owners, etc.). The people who gave us “lean production” long ago still have yet to own up to that.

“Lean production” missed some critically important elements of TPS. While today these elements are now more fully recognized, they remain less important in Lean that they are in TPS.

Together, I call these “the umami of TPS,” where umai (うまい) means “delicious” and mi (味) means “taste.” Without these, Lean can taste sweet some of the time, but most of the time there are strong tastes of sourness, saltiness, and bitterness – especially for employees who have been harmed by Lean.

Lean = TPS – umami

Add umami, “delicious taste,” to Lean and you come much closer to TPS. Please try that.

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