Author Archives: Donald Reinertsen

Technical Debt: Adding Math to the Metaphor

Ward Cunningham introduced the “debt metaphor” to describe what can happen when some part of software work is postponed in order to get other parts out the door faster. He used this metaphor to highlight the idea that such postponement, while often a good choice, could have higher costs than people suspect. He likened the ongoing cost of postponed work to financial interest, and the eventual need to complete the work to the repayment of principal, observing that the interest charges could eventually become high enough to reduce the capacity to do other important work. Continue reading

The Dark Side of Robustness

Nobody likes a fragile design; when you provide it with the tiniest excuse to fail, it will. Everybody likes robust systems. Robustness can be defined many ways, but I think of it as the ability perform as intended, in the presence of a wide range of both expected and unexpected conditions. Thus, a robust system is relatively imperturbable. Continue reading

The Four Impostors: Success, Failure, Knowledge Creation, and Learning

Some product developers observe that failures are almost always present on the path to economic success.  “Celebrate failures,” they say. Others argue that failures are irrelevant as long as we extract knowledge along the way. “Create knowledge,” they advise. Still others reason that, if our real goal is success, perhaps we should simply aim for success. “Prevent failures and do it right the first time,” they suggest. And others assert that we can move beyond the illusion of success and failure by learning from both. “Create learning,” they propose.  Unfortunately, by focusing on failure rates, or knowledge creation, or success rates, or even learning we miss the real issue in product development. Continue reading

Is One-Piece Flow the Lower Limit for Product Developers?

In Lean Manufacturing one-piece flow is the state of perfection that we aspire to. Why? It unlocks many operational and economic benefits: faster cycle time, higher quality, and greater efficiency. The economically optimal batch size for a manufacturing process is an economic tradeoff, but it is a tradeoff that can be shifted to favor small batches. We’ve learned to make one-piece flow economically feasible by driving down transaction cost per batch. One-piece flow is unquestionably a sound objective for a manufacturing process. Continue reading

Going to Gemba and Its Limits

It is important to go to where the action is taking place. I was taught this as a young officer in the Navy, where, as in other areas of the military, we emphasized “leading from the front.” In warfare the reason is obvious: it is difficult to assess a complex situation from a distance. The further you are from the action, the more your view is obscured by what the great military writer Clausewitz called, “the fog of war.” Continue reading

The Cult of the Root Cause

“Why?” is my favorite question because it illuminates relationships between cause and effect. And when we ask this question more than once we expose even deeper causal relationships. Unfortunately, my favorite question has been hijacked by the Cult of the Root Cause and been transformed into the ritual of “The Five Whys”. The concept behind this ritual is simple: when trying to solve a problem, ask “Why” at least five times. Each “Why” will bring you closer to the ultimate cause of the problem. Finally, you will arrive at the root cause, and once there, you can fix the real problem instead merely treating symptoms. Continue reading

Please Wear Your Clown Hat When You Celebrate Failure

A recent column in Wired magazine recounted the story of the 5,127 prototypes used to create the first Dyson vacuum cleaner. In this column, Sir James Dyson notes his similarity to Thomas Edison, who said, “I have not failed. I’ve just found 10,000 ways that won’t work.” Dyson appears to take pride in his 5,127 prototypes as emblematic of the persistence and fortitude of an entrepreneur. In contrast, I think this extraordinary number of unsuccessful trials may illustrate a very fundamental misconception about innovation. Continue reading

The Lean Approach to Context Switching

A great insight of lean manufacturing was recognizing the pivotal importance of reducing changeover costs. American manufacturers would run the same parts on their stamping machines for two weeks because it took 24 hours to changeover the machine. Along came the Japanese, who reduced the changeover time by 100x, and suddenly short run lengths became cost-effective. With shorter run lengths, batch sizes became smaller, and this improved quality, efficiency, and flow-through time. The great blindness of the American manufacturers was accepting the cost of changeovers as immutable. This condemned them to use large batch sizes. Continue reading

Why Do Iterations Work?

In product development we often use iterations to increase the quality and robustness of our products. Why does this work?

To begin, let me clarify my terminology. By “iteration” I mean covering the same ground twice. I do not use the term iteration to mean breaking a larger task into several smaller pieces; I call that batch size reduction. I must mention this because many people in the agile software community to use the term iteration to refer to breaking a project into a number of smaller pieces. It is a superb technique, but I consider it confusing to label it iteration. Continue reading

Boiled Frogs and Thought Experiments

Aristotle understood the value of thought experiments. They can be done quickly without get your hands dirty. Measurements are always precise and consistent. Results are perfectly repeatable. So, why bother with a real experiment when you can do a thought experiment?

Silly Aristotle. We are much smarter than that now. Perhaps. Management thinkers constantly quote the example of the boiled frog. Put a frog in boiling water and it will jump out. Slowly raise the temperature of the water and it will fail to notice the gradual change and boil to death. Since most of us lack both the frog and the insensitivity needed to do this experiment, like Aristotle, we accept the results of the mental experiment.

What would a real experiment reveal? The frog dies if placed in boiling water. The frog jumps out when the water is heated slowly. What happens if the frog is placed in freezing water? It will die. What happens if the temperature of the water drops slowly, such as from summer to winter? The frog will activate genes that produce metabolic enzymes that function at low temperatures.

As any dinosaur could tell you, slow change gives us time to react, rapid change can lead to extinction.


Fast Company: “Next Time, What Say We Boil a Consultant.” November 1995 (p. 20) The “boiled frog” story.