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  • Writer's pictureLean Quest


Through the years, Lean (Toyota Production System) has defined 3 sources of inefficiency. Outside observers of Toyota have traditionally only focused on eliminating/reducing waste, but those that have worked for any time within Toyota know that all 3 sources are critical.

The sources of inefficiency as defined by looking at the Toyota Production System (TPS):

  • Overburden – Muri (無理) – Unnecessary stress on people and or machines

  • Unevenness – Mura (斑) – Irregular volumes / Unlevel workloads

  • Waste – Muda (無駄) – Consuming resources without adding value

While at a high-level, the focus on Muda approach makes sense, there are even greater opportunities from addressing Over-burdening and Unevenness. Let’s take a closer look at the inefficiencies:


Overburdencomes from the overworking of people and machines. Anytime you ask a person or machine to do more than they are natural capable of doing. If you put 2-tons on a 1-ton truck it breaks down; if you over burden a person they breakdown. Over-burdening has a predictable impact:

  • Equipment breakdowns (skipped maintenance, overuse, over loaded, etc.)

  • Safety issues (not using safe procedures-lifting, not using PPE, equipment speed, etc.)

  • Quality issues (taking short cuts, skipping quality checks, miscounts, etc.)

  • Moral (frustration, absenteeism, etc.)

While sometimes you can surge and get increased speed for a short period of time, in the long-run safety, quality and moral issues end-up costing you more.

Unevenness – comes from irregularity in processing levels – peaks and valleys. This is generally related to volume of work or poor planning. Unevenness has predictable impacts:

  • At peak you have Overburdening, overtime, congestion, extra resources

  • In the valley you have unused resources, unpredictable hours, wasted space, and a lack of urgency to complete the work (work always fills the time allotted)

Unevenness is particularly bad because:

  1. It causes Overburdening during peaks

  2. It causes an erosion of the overall capability / efficiency in the valleys

  3. It makes planning and managing the operation more difficult

Wastecomes from processes that consume resource without adding value (or more resource than necessary). Taiichi Ohno defines the standard seven wastes as:

Over-production is considered the worst waste because it causes the other wastes and is often used to hide problems (producing extra, just in case).


Waste is easiest to address at the process level because it is more visible. In fact, most organizations have made some effort to identify and eliminate wastes from their processes. Eliminating process waste has an undeniable positive impact. Wastes also exist at the system level, but these are harder to see and often go unaddressed. Isolated activities to reduce waste will work in the short term, but in the long term do not address the root cause(s).

Unevenness has the most dramatic effect at the system level. It can come from a variety of sources; however, the most common being large fluctuations in volume. The organization needs to understand and differentiate between actual and created demand customer demand. This requires the gathering and detailed analysis of data – the concept of Know Your Business (KYB). This analysis may include volume and productivity information by day, shift, process, week, month, order type, ship method, and other relevant criteria.

Once collected, we need to ask ourselves, what actions are available to shift this volume around to achieve a more Level and Balanced operation with reduced Overburdening. The typical reaction to this is …

“This is impossible”

“We can’t change customer demand”

“Our system can’t handle this”

Usually without ever investigating the possibilities. We have to challenge ourselves. There is too much to gain. While challenging to achieve perfect Level and Balance, any

improvement will result in less Waste, higher productivity, fewer occurrences of Overburden, and an operation that is much easier to plan and manage on a daily basis.

When the effects of Waste and Unevenness go unaddressed, the result is often Overburdened people and equipment. This Overburdening breaks down the people and equipment causing frustration and making it difficult to run a consistent operation.


Most organizations have a fundamental understanding of how to go about identifying and eliminating waste in their operations. However, there is a general lack of understanding as to the importance and the interdependent relationship of Unevenness and Overburdening.

While difficult to accomplish, addressing Unevenness at the system level is needed to identify the true root cause.


As you look to improve the efficiency of your operations, are you asking the right questions:

  • Do you focus on waste at the system level as well as the process level?

  • Do you understand the relationship between Overburden, Unevenness, and Waste?

  • Have you engaged your customers / suppliers in efforts to reduce Unevenness? Were they successful?

  • Do you manage Unevenness or are you a victim of it?

What can you do now that will help you reduce inefficiencies in the future?

How can Lean Quest help you in the future?

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