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Category: Case Interview Mastery for McKinsey, BCG, Bain
The Craft and Art of Brainstorming in MBB case interviews
Written by Dr. Sidi S. Koné
How to show outstanding brainstorming and idea generation capabilities during MBB Case interviews
Mastering brainstorming is an extremely rare skill with candidates who interview at MBB. But if done right, showing strong brainstorming skills is an enormously powerful way to set yourself apart from practically all other applicants who interview with McKinsey et. al.! And by the way – it will also serve you massively during your career as a top strategy consultant!

Brainstorming questions usually come in the form of
  • “How can we achieve XYZ?”
  • “How should we react to ABC?”
  • “What could be reasons why XXX has happened?”
Contrary to the common perception, and contrary to what you might have heard/learned in university, Brainstorming in Strategy Consulting does NOT mean to shoot out all sorts of ideas as they come to your mind! In fact, this is the worst thing you could ever do in an MBB interview! Please… don’t do this!

In Strategy Consulting, Brainstorming is a very methodical and structured process. In its purest essence, it is an exercise in logic tree building! Starting from the focal question, you need to break this question down into its constituting elements. You do this by using a logic tree, where each branch represents a driver. Amongst these drivers, the ones which you can influence are called “levers”.

So, you first write down the precise question. This means, you split the key question into sub-questions. These sub-questions are then further split into drivers and levers. All of this is done by means of a logic tree. Once this is done, THEN you can start developing ideas on
  • How you can influence each lever into the desired direction (if the question was “how can we achieve XYZ?”)
  • How you can prevent a threat posed to the drivers of your focus metric (if the question was ”how should we react to a certain competitor move?”)
  • What could be reasons for an observed phenomenon (if the question was “why has XYZ happened?”)
Let’s look at a concrete EXAMPLE: 

Imagine we are discussing a situation where the Ministry of Education in a developing country has asked the question:
“How can we improve the quality of primary education in our country?”
Most candidates will then start to generate a, more or less structured, list of concrete ideas – shooting essentially from the hip (e.g., “They could invest into more teachers!”). 

Some candidates will take some time to bucket these ideas into categories (“There could be short term measures and long term measures. Short term measures could for example be blablabla…”). This is a bit better – but still far from good! 

You have to realize that brainstorming is not just about the ideas themselves (in fact, it is not even primarily about the ideas!), but first and foremost about HOW you generate these ideas! You want to demonstrate the rigor of your thinking, as well as the ability to outline and articulate this thinking in a sharp way.

So here is how a very strong candidate develop his answer to this brainstorming question (please look at the diagram below!):

Step 1: Outline the precise question – “How can we improve primary education in country X?”

Note that this question is impossible to answer before having precisely defined, what “quality of primary education” actually means! It could be number of children going to school… Or number of graduates produced by the system… Or how good the pupils are… etc. A blurry question like “How to improve…” MUST be defined! And it is the candidate’s duty to nail down the interviewer on the definition of what we are solving for – the FOCUS METRIC! 

So let’s assume, the interviewer confirms that the focus metric is “number of children going to school”. Only now we can proceed!

Step 2: Disaggregate the question – build the logic tree and identify what drives the answer to the question. 

So we could imagine that the primary reasons for NOT sending children to school would be of financial nature, logistical nature, and potentially cultural nature. Then you develop the tree into a set of sub-branches which further disaggregate these three categories into sub-reasons. If we can do something about these sub-reasons, then they are “levers” which we can pull!

Step 3: Develop ideas – NOW is the time for the actual ideation! Outline concrete examples on the actual measures which could influence each lever into the desired direction.

THIS is how you brainstorm! Define the focal question, disaggregate this question into its constituting elements, and then outline concrete examples underneath each (sub-)element which could answer the main question.
Let's look at another EXAMPLE: 

We could address the following question in a similar way:
“What could be potential reasons why our client's main competitor has decreased prices last year?”
Following the above outlined 3-step-approach, we could come up with something like this (see exhibit below). 
This showcases MUCH richer thinking than what 99% of candidates would be able to come up with in an MBB interview when following the advice from typical case preparation books!

We hope this helps you understand, how you can really stand out from the pack and AMAZE your interviewer at McKinsey, BCG, or Bain.

How we can help you break you into McKinsey, BCG, or Bain

If you, as an applicant at one of the big strategy consulting firms, would like to learn how to ensure success in your interviews with McKinsey, BCG, or Bain, then feel free to apply for a free initial consultation with us. In this free session we will find out whether we can help you, and if so, how we can help you to reach your goal of joining a firm like McKinsey, BCG, or Bain & Company. 

Within the last years, we have helped more than 350 people to receive job offers from the three MBB companies! On average, every single week, two of our clients are signing an employment contract with either McKinsey, BCG, or Bain.

About the author: 
Dr. Sidi S. Koné

Former Senior Engagement Manager and Interviewer at McKinsey & Company | Former Senior Consultant at BCG

About The MBB Offer Machine™

We help aspiring graduates, young professionals, and seasoned topic experts to ensure success in their job interviews with the world's most reputable Strategy Consulting Firms.

We place a special emphasis on "MBB":
  • McKinsey & Company
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About the author: 
Dr. Sidi S. Koné

Former Senior Engagement Manager and Interviewer at McKinsey & Company | Former Senior Consultant at BCG

About the author: 
Dr. Sidi S. Koné

Former Senior Engagement Manager and Interviewer at McKinsey & Company | Former Senior Consultant at BCG
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