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Don’t overdo that MECE thing – make your ideas independent and collectively exhaustive

Jun 14, 2012

This is part 3 of our 4-part on MECE thinking — part 1, part 2, part 3, and part 4.For those of us discovering the MECE concept and those perfecting it, it can be oh-so-attractive: Finally, a way to organize my thoughts! It’s simple and elegant. The acronym is even catchy. Why didn’t I hear of this before? This is it! Douglas Adams was wrong: 42 isn’t the answer, MECE thinking is!

And, to be fair, pushing your thinking toward being more MECE usually pays high dividends. But not always. In fact, many times, when we say MECE, we really mean ICE (independent and collectively exhaustive).

Usually you want your answers to be ICE—independent and collectively exhaustive—not MECE

ME stands for "mutually exclusive," or "no overlaps"; CE stands for "collectively exhaustive," or "no gaps." The spirit of the guideline "think MECE" is consider all possible answers exactly once: consider each at least once (CE) and at most once (ME). In this context, "no overlaps" is primarily a measure of efficiency: If you’ve already thought about something once, don’t consider it again. Doing so requires additional effort and reduces the clarity of the classification.

Now, strictly speaking, events are mutually exclusive if the occurrence of one precludes the occurrence of another. But in most cases this preclusion isn’t what you should be after. Consider the standard example of increasing the profitability of our company:

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MECE vs. ICE – The initial breakdown of a profitability question map shows two independent, rather than mutually exclusive, options.

This is the school-case illustration of a MECE-thinking pattern trumpeted by management consultants across the globe. Yet, strictly speaking, it isn’t MECE.

Of course increasing revenues is one way to increase one’s profitability, and so is decreasing costs. In fact, they are the only two ways to do so, so the framework is CE. So far, so good.

But it isn’t ME, because you can attempt to increase revenues and also attempting to decrease costs. For instance, you may increase your revenues from new clients and reduce your variable costs at the same time. Doing one usually doesn’t preclude you from doing the other. So these ideas aren’t mutually exclusive, they are independent.Here we don’t define independent in a probability-theory meaning way—two events are independent if the occurrence of one doesn’t affect the probability of occurrence of the other. We define it as "distinct": Doing what one node advises—say, increasing your revenues from returning clients—does not require you to do another node.

Now, you might object that with limited resources you might be able, at any given time, to pursue just one avenue, which makes your elements mutually exclusive. That’s fine, but that’s just a technical limitation; it shouldn’t be a philosophical standpoint of yours, because what should interest you isn’t only solutions that would each require all of your resources.

To be sure, let’s think of a truly MECE set of answers to our increase-our–profitability problem.

By adding ‘only’ in my branches, I’m bringing the preclusion aspect: if I choose one, I can’t also pursue the other. As a result, these nodes are indeed truly mutually exclusive, not just independent. But they are no longer collectively exhaustive, because the hybrid option is still a logically valid answer, so I need to add that one, too.

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You can force the nodes of a question map to be truly mutually exclusive. However, it's unclear that you should want to do so.Now, is this question map any better better than the first? To answer that, we need to see what we've gained from adding the preclusion clause. Not much. In fact, I’d contend that we’ve lost something because that middle branch has re-tangled together the two elements of profitability, revenues and costs, that we already untangled. So, I'd contend that that new structure is a lot less insightful than our original one.The spirit of "be ME" is "no overlaps in your answers." But you achieve that with nodes that are independent, whether they are truly ME or not. So you don’t want the nodes to be MECE, you want them to be ICE, or, well, rICE—really ICE.Sometimes you don't want to be ME – There is a case against MEness“We need a team with a MECE skill set.” No you don’t.Here again, I have no problem with the CE part. It’s the ME part that clashes: so if someone on your team speaks one language, will you preclude anyone else that also speaks that language? How are you going to communicate? You certainly don’t want people with mutually exclusive skills.Quite the contrary. You would hope that everyone spoke the same language. Likewise, if your team is a bunch of people building a bridge, you’d hope that more than one person knows civil engineering, so that they can, for instance, check each other’s maths. Redundancies can be desirable, or, indeed, necessary.Take the late Berkeley professor Martin Landau’s particularly colorful example: He once sat on a plane that was forced to make an emergency landing. After they landed safely he asked the pilot what happened. It turned out that the rudder was defective. So Landau asked how the pilot managed to land the plane. “He replied that he had been able to compensate for the impairment of the rudder by utilizing additional features of the aircraft. There were, he said, safety factors built into all planes.”In a more recent and, tragically, deadly example, Boeing's design of the 737 Max MCAS system has come under fire because it relied on a single sensor. In some industries, aeronautics being one, you want to have some redundancies.And that brings us to a favorite saying of my former boss, professor Paula Sanders (paraphrasing): "We like redundancies, as long as they’re intentional." Right on!So, in summary, although consultants speak about MECE thinking, what they often mean is ICE. So you should have a clear understanding of what's MECE and what's ICE. Besides, ICE is, of course, … cooler.This is part 3 of our 4-part on MECE thinking — part 1, part 2, part 3, and part 4.ReferencesBaker, Mike and Gates, Dominic. "Lack of redundancies on Boeing 737 MAX system baffles some involved in developing the jet." Seatle Times, March 26, 2019. Retrieved November 24, 2019.Chevallier, A. (2016). Strategic Thinking in Complex Problem Solving. Oxford, UK, Oxford University Press, pp. 58–67.Landau, Martin. “Redundancy, Rationality, and the Problem of Duplication and Overlap.” Public Administration Review 29(4) (July-August 1969): 346-358.van Gelder, T. (2010). "What is MECE, and is it MECE?". Retrieved October 4, 2014, from https://timvangelder.com/2010/06/04/what-is-mece-and-is-it-mece/.Image credit: Hans/Pixabay.

Arnaud Chevallier