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Category: Case Interview Mastery for McKinsey, BCG, Bain
Case Interview Mastery: 
“The Five Commandments” of Chart & Data Interpretation
Written by Dr. Sidi S. Koné
HOW TO ANALYZE CHARTS, TABLES, AND GRAPHS DURING CASE INTERVIEWS WITH MCKINSEY, BCG, OR BAIN & COMPANY
When interviewing with McKinsey, Boston Consulting Group (BCG), or Bain & Company, many candidates struggle BIG TIME with analyzing tables and charts/graphs. They have trouble with prioritizing when there is a lot of information, and they have a hard time to come up with non-obvious insights.

This is indeed a problem - because effectively interpreting data and information is one of the crucial success factors in case interviews conducted by McKinsey, Bain, or BCG. Very often, this data comes in the form of graphs or charts which the interviewer shares with the candidate at some point during the case. Finding the central insight of the chart, the ‘so-what’, is the single most important quality you will have to show in this situation!

Thank god there are a few best practices which, if properly conducted, will massively help you to impress the interviewer in this domain! 

We call them “The Five Commandments” of Chart & Data Interpretation, and they form a central pillar towards achieving "offer-readiness" for McKinsey, BCG, and Bain.
Let’s go through them one by one…

1 Take TIME!

The first thing you should do when presented with a table or chart is to take time to properly scan the information provided. In fact, you should ideally have a “standard phrase” such as

“Thank you! I see, there is quite some information on this chart. So let me take a brief moment to quickly scan the information and identify…

…which steps we need to take to determine X” (if the interviewer has asked you a concrete question like “How to derive XYZ from this data?”)

…how we should proceed” (if the interviewer just gave you the chart but asked for no concrete analysis)

This is a very frequent Achilles’ heel with candidates! It is a pretty widespread problem that candidates tend to put themselves under time pressure and start talking before even having properly looked at the chart! The consequence is that you are not crisp in your messages, you’re just “wobbling around”, starting sentences without knowing how you will actually end them, etc. This leaves a very bad impression!

Interviewers at MBB actually TEST for whether you have the maturity to take the space that you need in order to conduct a proper analysis! 

Just understand it from the interviewer’s perspective: as a project manager, the last thing I want to have on my team is a young colleague who tends to talk before thinking! This would represent an enormous risk in client interactions and can undermine credibility of the whole team, or even the whole firm!

What leaves a much better impression is to confidently announce that you will need a moment to
  • Take in the information on this chart
  • Link this information to what has been discussed to this point
  • Suggest the best way forward
Another reason for taking time is that it allows you to verify/clarify your understanding of the information given. Very often, e.g., unit abbreviations are not entirely clear (or even lacking!). Taking a moment after receiving the chart will allow you to scan these elements and clarify their meaning with the interviewer – before you start discussing observations and insights!

2 Scan the base parameters (“Read the chart correctly!”)

This is tightly related to the previous point of taking adequate time. Oftentimes, candidates do not pay attention to what is actually shown on a chart, hence they are not properly grasping the parameters and what they actually describe! A couple of habits are important when reading a data table or chart. 
  • It starts with reading the title (this sounds trivial, but oftentimes just properly reading the chart title would have prevented candidates from stating obvious nonsense!)
  • ​Look at the labels and units of measurement (frequent source of misreading charts!)
  • ​Identify whether and which dependencies are shown on the chart (just properly checking what depends on what is oftentimes a very effective way of preventing yourself from completely unnecessary instances of misreading data! For example, in a x-y-axis chart, the vertical metric (y-axis) usually depends on the horizontal metric (the x-axis), and NOT the other way round!) 

3 Identify key observations

The key messages (the ones that are relevant for the client’s question) within data and charts are usually found amongst the following:
  • Static relations
  • ​Trends
  • ​Correlations
  • ​Breakdowns
Let’s look at each of these points.

  • Static relations
Ususally a simple comparison of values (comparing one number or group of numbers to the others - often a bar or a line chart), e.g.,

  • Comparing client metric vs. market average or vs. competitor
Here, a key observation could be: 
“The client’s profit margin is 30% below strongest competitor.”
  • Comparing one scenario vs. another scenario (e.g., “Outsourcing is 20% cheaper than in-house production.”)
Here, a key observation could be: 
“Outsourcing is 20% cheaper than in-house production.”
  • Trends
  • Specific number or group of numbers showing growth or decline 
Here, a key observation could be: 
“Revenue has grown by about 10% over the last three years, however profits have halved during that time frame.”
  • Rate of change compared to other logically related numbers (e.g., “Sales volume drops by 20% for every 10% increase in price.”) 
Here, a key observation could be: 
“Sales volume drops by 20% for every 10% increase in price."
  • Correlations
  • Specific relationships between two or more numbers; such correlation can be geared towards the same direction (positive correlation) or in divergent direction (negative correlation)
  • Breakdowns
  • Oftentimes, even if Totals seem to show a consistent pattern, digging deeper into specific segments will reveal certain “hidden shifts"
Remember our example about the two scenarios - Outsourcing vs. In-House production. At the surface, we saw that outsourced production is significantly cheaper:
However, if we do the breakdown and split the production cost into the different sub-segments, then we might see something like this:
For Outsourcing, the decrease in total production cost is mainly driven by decreases in labor cost and material cost. However, these decreases are partly offset by significant increases in logistics costs which occur if we decide to outsource. 

And such shifts remain completely hidden if we only look at global average numbers! This is why breakdowns oftentimes lead to very important observations.
Spotting those kinds of patterns quickly is vital. When you are given two or more charts at the same time, the key message usually becomes evident by combining them. Again, here you might need to take appropriate time! 

4 Turn observations into insights & avoid “spontaneous amnesia”!

One of the most amazing observations we have made over the last couple of years is the following:

Many candidates, as soon as they get a chart or data table, fall victim to what you can call “spontaneous amnesia”! This means, they immediately forget EVERYTHING that has been discussed leading up to this chart!

So they tend to stare at the chart, drowning in the information, and trying to distill insights JUST by looking at all the information on the chart. 

But they DON’T CONTEXTUALIZE the chart! 

This means, they do NOT relate the information on the chart back to the core question, the criterion to answer this core question, or to the last insight generated BEFORE the chart was given out by the interviewer.

So, there is a simple trick: as soon as you receive a chart or data, your IMMEDIATE mental reaction should be: 

“Wait, what did we just discuss, that led the interviewer to give me this data now?”

This is often already sufficient to point you to the central insight of the chart!

You must be guided by the LOGIC which allows you to answer the core question, and the chart should just work as a source of information to perform the required corresponding analyses.

!!! Do NOT be guided by the chart itself !!!

Because very often, not all information on graphs you get is insightful or important! Parts of the information in the charts are crucial, others just create noise to distract you. Taking your LOGIC as the guiding star will allow you to quickly identify which pieces of information are crucial to generate the required insights to proceed towards an answer to the client question.

Let’s quickly look at one example…

- - - - - - EXAMPLE - - - - - -
Let's assume we have a Private Equity client. 

They are looking to potentially acquire a specific target company. The acquisition price would be 500m USD. And their goal is to maximize returns, with a minimum requirement of 50% return-on-investment (RoI) within 5 years.
Now let's assume we receive the following chart:
A poor way of dealing with this chart would be to only concentrate on observations. E.g., looking at this chart and saying:
"We can see that the company value is related to the annual EBIT. So for every 20-percent-increase of EBIT, the company value will increase by around 120m EUR!"
This is NOT an insight! This is just an observation - but it is NOT contextualized! It is essentially just reading out what you see here. But it is not relating it back to the case context and to what the client has asked.

So what do we mean with "contextualizing the chart"?

We know already that the client's goal is a return on investment of at least 50%. And we know that the acquisition price is 500m EUR. So we can infer that the goal (50% RoI) will be achieved if the client could re-sell the target company for at least 750m EUR. 

So if we link this now to the information on the chart, we may realize the following:
We see that 750m EUR company value would be achieved if the target company is brought to an annual EBIT of more than 125m EUR. So if the client is confident that they can bring the target company to this EBIT level of 125m EUR per year, this deal would make financial sense for the client!

THIS is an insight! Because it relates clearly to what the client has asked, and what we need to find out in order to answer the client question!

5 Exhibit top-down communication and propose next steps

Insights and findings should always be communicated in a top-down way! When analyzing a chart, this means:
  • Start your communication with the key insight that you identified from the chart (see above for the difference between insights and mere observations!).
  • ​Then, give the reasons for your conclusion. These reasons must be underpinned by the data and information from the chart (and oftentimes also by combining this data with information you received earlier)!
  • ​Based on the insight generated, proactively suggest (without having been asked by the interviewer!) the logical next step in your navigation through the case in order to proceed towards reaching a recommendation/answer for the client! 
Let’s look a bit closer at the first two points: communicate insights, and then give the reasons. This is what is widely referred to as “The Pyramid Principle”. Here is a depiction. 
Even though you typically DERIVE insights in a bottom up way, you should always COMMUNICATE these insights in a top-down way. 

So after you have taken adequate time to scrutinize and understand a chart, you should start your communication to the interviewer with the main insight (sometimes also called “the takeaway”). This insight is usually supported by one or several observations. 

We just discussed the difference between observations and insights - observations usually SUPPORT the central insight of a chart. And these observations in turn are rooted in the actual data and information that can be found on the chart you have been handed.

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 you can can build this skill of interpreting charts and data in an absolutely superior way, 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
  • ​Boston Consulting Group (BCG)
  • ​Bain & Company

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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