MECE is a list. It is a list of qualities lists should have. According to MECE, any list should be
- Mutually exclusive – the members of the list should “exclude” each other, i.e. be distinct
- Collectively exhaustive – the members of the list should “exhaust” the relevant field, i.e., contain everything that belongs on the list.
In plain English, MECE says that a list should have
- No overlaps
- No gaps
MECE widely used by management consultants. In fact it seems to have acquired the status of holy writ. According to Ethan Rasiel in The McKinsey Way:
MECE…is a sine qua non of the problem-solving process at McKinsey. MECE gets pounded into every new associate’s head from the moment of entering the Firm. Every document (including internal memos), every presentation, every email and voice mail produced by a McKinsey-ite is supposed to be MECE. Ask any number of McKinsey alumni what they remember most about the way the Firm solves problems and they will tell you, “MECE, MECE, MECE.
It is therefore interesting to ask whether MECE is adequate, even by its own lights. So we should ask:
- Does MECE have any overlaps?
- Does MECE have any gaps?
It seems clear that gaps and overlaps are very different, so MECE looks to be ME. But is it CE? We need to ask whether there are any properties that a properly formed list should have over and above ME and CE.
And obviously there are. For example, what’s wrong with the following list?
- Bashful
- Doc
- Dopey
- Grumpy
- Hannibal Lecter
- Happy
- Sleepy
- Sneezy
The list is ME – all items are genuinely distinct. And it is CE – it “exhausts” the relevant field, which is the seven dwarfs. But it is clearly a stupid list. It violates the commonsense principle that lists should not include things that don’t belong on the list.
And it is not too hard to think of other desiderata which are missing from MECE.
So MECE is not merely not MECE. MECE is obviously not MECE. MECE does not live up to its own standards.
MECE, for all it’s usefulness, is not and never was meant as the be all and end all when judging work product. I only had two years of Latin in middle school, but I still know that something can be “sine qua non” yet also “necessary but not sufficient.”
No consulting rubric, no framework, no template is worth a wooden nickel if the consultants wielding them don’t apply their own intelligence and common sense.
Ethan, Thanks for that. You’re quite right that every guideline for thinking has to be applied with intelligence and commonsense. Still, I think you are agreeing that MECE is not MECE, which it should be, at least within McKinsey, if everything should be MECE. Also, the very next sentence in your book says “MECE structures your thinking with maximum clarity (hence minimum confusion) and maximum completeness.” If MECE is merely a “sine qua non” then it alone can at best *help* thinking have maximum clarity and completeness. Other principles are needed as well – some of which should have been included in MECE if MECE was MECE.
Tim, you’re the philosopher, not I, but it seems to me that you have made a category error. MECE is a rule for work product (awful term that, though I’ve now used it twice), not a work product (arrgh, three times!) itself. One could, I suppose, come up with some sort of Grand Universal Theorem for documents, but the acronym would be ever so unwieldy.
As to my statement on clarity and completeness, I think it stands: lack of overlap means no confusion among elements; no gaps means nothing essential left out. If you then want to add something about, say, “Nothing Extraneous”, thus weeding out Dr. Lecter, and, perhaps, “High Value Only”, and, for good measure, “Fully Implementable”, then you end up with MECENEHVOFI. I don’t think this, or any other acronymic construct I could come up with after a few hours of deeper thought, would be all that useful to practitioners.
Ethan, as is often the case, there’s a purely semantic or definitional aspect to this. I took MECE to be “a list of qualities lists should have,” whereas you I think are taking it to be something like “a handy list of a couple of the most important qualities lists should have, handy in part because it has a useful acronym.” Fair enough. MECE-hood certainly is relative to the nature or definition of the list, or what we would call the “grouping principle.” The really substantive point is not the MECE-hood of MECE, but what are the criteria for well-formedness of lists or groups? ME and CE belong, as does NE (Nothing Extraneous), and you’ve added some more. Another important one I think is that a list should be Ordered, i.e. the elements listed in some natural or sensible order. What others?
The acronym’s almost there…
O rderred
N othing
E xtraneous
L inked
I nclusive
S separated
T hemed
well… almost :)
Craig, not bad at all. A lot of those things (ordered, linked, themed) would be subsumed under Minto’s Pyramid Principle, which is part of McKinsey’s “basic training”. I don’t have time to check (heading to the airport in a few minutes), but I’m pretty sure MECE comes from Minto. It’s certainly in there, even if she doesn’t use the term explicitly.
There’s no doubt that MECE is a shorthand. It’s most useful as a very quick check of document structure. It’s usually easy to spot if a document is not MECE, which means it gets sent back for reworking and — if necessary — rethinking.
Barbara Minto refers to MECE in ‘The Pyramid Principal’ (1987). In chapter 7, in the section on Structural Order, she writes:
“When you divide a whole into its parts – whether it be a physical whole or a conceptual one – you must make sure that the pieces you produce are:
- Mutually exclusive of each other
- Collectively exhaustive in terms of the whole.
I abbreviate this mouthful to MECE, but it is a concept you no doubt apply automatically every time you create an organization chart”
She continues with further examples and explanation.
Minto may have put a nice acronym on it, but the MECE principles are a lot older than that. They come up a lot in my area of ontology and are clearly formulated at least as far back as the 13th Century by John Duns Scotus.
Have a look at paragraph 1.4 of “A Treatise on God as first principle”, here: http://www.ewtn.com/library/theology/godasfir.htm
Speaking of which, the ridicule of lists (categories) is also a long running practice. Foucault of course made famous Borges’ satire of “a certain Chinese encyclopedia” which states “animals are divided into: (a) belonging to the Emperor, (b) embalmed, (c) tame, (d) suckling pigs, (e) sirens, (f) fabulous…”
cheers,
RdR
Thanks Richard for digging up the Scotus reference. I was aware that these principles went a long way back but didn’t have a specific text to point to.
Interestingly, Scotus goes beyond MECE in listing not two but three qualities lists or “divisions” should have:
“1.4 For a division to be clear it is necessary (1) that the members resulting from the division be indicated and thus be shown to be contained in what is divided, (2) that the mutually exclusive character of the parts be manifest, and (3) that the classification exhaust the subject matter to be divided.”
Obviously (2) is ME and (3) is CE – indeed he uses that same language! [as translated, of course]
Principle (1) is a little obscure but I think it might be, in fact, the “Nothing extraneous” point which I raised in the original post.
In other words, to point to another fundamental principle: There’s nothing new under the sun!
This is nonsense. A partition of the sample space is one thing. The attributes of the partition is another.
MECE does not partition a sample space, so it cannot succeed ot fail as a partition of a sample space.
Michael,
Could you clarify a bit more how you see the difference between “partitioning” and “the attributes of a partition”?
I take it from the “one thing… another” phrasing that you see some fundamental distinction in the context of a collection of entities, but I’m not entirely sure what it is.
When I was taught the Pyramid Principle, we learnt that the items in the list needed to be not only MECE, but also of the same type.
It is this that sorts out the cannibal from the dwarves, rather than MECE itself. It is the essence of Scotus’ first test.
Creating a MECE list becomes harder when dealing with more nebulous ideas, as becomes necessary when doing Issue Analysis on topics such as whether a company should invest in sales in a certain territory. Interminable discussions on flip charts and whiteboards can ensue.
MECE is only a small part of the tool set. It just checks whether the conceptual space has been partitioned in a way that leaves no gaps and has no overlaps. It doesn’t tell you anything about what should be in that space, or where the dividing lines should go. That is left to the intelligence of the users, applying other methods.
[...] amount of um’s and ahh’s. Maybe we all should take a course from McKinsey’s MECE voicemail training, but alas, we all end up rambling, stuttering, and fucking it all up. My best advice is to call, [...]
Hello,
Thank you for the interesting discussion.
If I may offer a further point of view (from a former quant lost in business), MECE can be viewed also as the partition concept of probability theory.
The McKinsey definition may not be completely sound but it works well enough, which pragmatically is all I care in a business context.
On the other hand, I do share and appreciate the point of view of a sound skepticism on this kind of tools.
Going back to the far more interesting and elegant domain of probability theory, there, partition (MECE) is the cornerstone of the whole cathedral.
Probability is how we think (even more in the bayesian and de Finetti sense, or Savage sense for an Anglo-saxon reader). Probability is driving the latest successes in narrow AI (from translation to IBM’s Watson system)
It is a wonderful building, so partitions must have some special and deep connections to what we are as thinking beings and (future) creators of thinking machines.
Great blog!
DD
Too funny.
I just read some of the comments above (I should have read them ALL before posting).
Just two additional points:
1 – I’m not the voice-mail leaving guy
2 – I agree with Michael. Partition and MECE share a form but they’re “orthogonal” in relation to the attributes.
…yet again, partitions can be “colored” and this starts a link with logic, graphs and hierarchies which is again running deeply in both the way we think and computer science.
DD
[...] Of course it is worthwhile considering that like all frameworks MECE has limitations. Look at the writings of Tim van Gelder on What is MECE and is it MECE. [...]
Dimittrij,
I think we all empathise with your pragmatism — at least as far as having experienced the need for it. However, you probably don’t mean stopping to look for improvements to theory or its application.
“Partitions” are a cornerstone to conceptual thinking beyond probability. In ontology, partitions have a long history under the heading “mereology” (the theory of parts and wholes) and stretch even further back to Aristotle, especially in his piece “Categories”, but also in the “Physics” and “Metaphysics”. One of the important aspects is that almost any predicate creates a category or partition. So, partitions or categories ends up being a study of the nature of things — often in terms of bundles of predicates. “Carving up the universe at its joints” as ontologists put it.
Note that even pragmatically, MECE is incomplete. Tim pointed out “nothing extraneous”, but Scotus also has an antecedent — namely that something has to be “indicated”. What Scotus points to is that you can have a false MECE: it may look exhaustive and nicely partitioned, but the subjects are not indicated by the labels… the predicates don’t apply. Think “phlogiston”, “phrenology”, “therapeutic touch” and the like. Or, in applied probability (i.e. risk management), dare we talk about “expert score cards”?
Tim it seems to me you went too easy on the ME portion of MECE … without getting into the discussion of whether not being ME and CE somehow compromise MECE’s value, can’t one argue that the slightest possibility of something being both mutually exclusive AND collectively exhaustive preclude ME and CE being mutually exclusive? In fact you could almost argue that they are *by definition* not mutually exclusive, otherwise the concept as a whole would be useless … or am I oversimplifying this??
btw I have an interview for an Associate position with McKinsey coming up next week, let’s see how far this kind of thinking gets me ha!
Hi Amir, A provocative comment, but I think I’m having difficulty grasping your point. Certainly if MECE is to be MECE, then ME and CE ought to be mutually exclusive of each other. It seems to me that they are, but just what it is to be ME is, generally, not very clear. In some simple cases it is clear enough (are Switzerland and Germany ME, geographically? presumably they are) but often in my travels I’ve looked at items in some kind of more abstract or conceptual list, and wondered what it would mean for those items to be ME. It is probably not a question that has any kind definitive answer. Good luck with the interview. – Tim
Hmmm I wasn’t very articulate … that doesn’t bode well for the interview.
What I was trying to say is, while you concede that ME and CE are mutually exclusive but argue that they are not collectively exhaustive (for MECE’s purpose), I’m wondering how they’re even mutually exclusive. To say that they are suggests that there is no overlap between ME and CE, yet from one perspective the reason for MECE’s being is to guide people to achieve maximum overlap in this regard, i.e. make lists/subcategories that are both ME and CE.
Essentially what you argued is that if one were to make a list of what qualities good lists should have, it would need to have more qualities listed than just ME and CE in order to be considered complete i.e. exhaustive (CE). I’m contending that, as items on that list, ME and CE aren’t even mutually exclusive … if they were, it would negate the very purpose of the MECE mantra.
I do however agree with you that there is some degree of subjectivity involved in defining what it means to truly be mutually exclusive, and we are quite possibly just defining it differently.
It’s just a guideline, and a very solid one. All guidelines require common sense and intelligence to determine the quality of the output. The McKinsey approach to brief engagements (developing 3 solutions that are MECE) is simple and effective, rather than complete and extensive.