9.1 Why Structure Matters
Most case problems are too broad to solve directly. Structure turns a large question into a sequence of manageable questions.
For example, if a client asks whether to enter a new market, you might examine market attractiveness, competitive position, economics, capabilities, and risks.
Purpose: A good structure tells you where to look, what evidence you need, and how the pieces of analysis will combine into a decision.
It also gives the interviewer an early view of how you think. A clear structure creates confidence that your later analysis will be disciplined.
9.2 What MECE Means—and What It Does Not Mean
MECE stands for mutually exclusive and collectively exhaustive. It is a useful principle for organizing a problem.
Mutually exclusive: Categories should overlap as little as possible.
Collectively exhaustive: Together, the categories should cover the major drivers of the problem.
MECE is a tool, not a goal in itself. You do not need to create perfectly theoretical categories every time. What matters is whether your structure is clear, useful, and complete enough to solve the case.
9.3 Creating Mutually Exclusive Categories
Mutually exclusive categories reduce duplication. If the same issue appears in several branches, your analysis may become repetitive or confusing.
For example, you might divide revenue into price and volume. Those are distinct drivers. By contrast, categories such as “customers” and “sales” may overlap heavily because customer behavior often directly affects sales.
Practical test: Ask whether a major issue clearly belongs in one branch rather than several. If not, refine the categories.
9.4 Creating Collectively Exhaustive Categories
A collectively exhaustive structure covers the major factors that could determine the answer.
If you analyze only revenue when the client’s problem is declining profit, your structure is incomplete because costs also matter.
This does not mean listing every imaginable factor. Focus on the categories that could materially affect the objective.
Useful question: “If all of these branches were fully understood, would I have enough information to answer the client’s question?”
9.5 Organizing Questions into a Logical Issue Tree
An issue tree breaks a main question into smaller questions that can be investigated separately.
Suppose the governing question is: “Why has profit declined?” One branch might examine revenue and other costs. Revenue could then be divided into price and volume, while costs could be divided into fixed and variable costs.
Good issue tree: Each level answers a more specific question than the level above it.
Avoid creating branches that are merely topics. Phrase them mentally as questions you need to answer.
9.6 Driver Trees Versus Issue Trees
Issue trees organize the questions that must be investigated. Driver trees show how an outcome is mathematically or causally determined.
For example, a revenue driver tree might show:
Revenue = Price × Volume
Volume might then depend on the number of customers and purchases per customer.
Difference: Use an issue tree to organize an investigation and a driver tree when you want to understand what variables mathematically or operationally drive an outcome.
The two approaches often work together.
9.7 Mathematical Versus Conceptual Structures
Some problems can be structured mathematically. Profitability is the classic example because profit can be decomposed into revenue and costs.
Other problems require conceptual structures. A market-entry decision might consider market attractiveness, competitive position, economics, capabilities, and risks.
Best approach: Use mathematical decomposition when the problem has a clear equation. Use conceptual categories when the decision depends on qualitative and quantitative factors that cannot be captured in one formula.
Do not force a mathematical tree onto a problem where it does not fit.
9.8 Making a Structure Specific to the Client
Generic structures are easy to recognize. A stronger structure reflects details from the case prompt.
If the client is a low-cost airline considering international expansion, your structure might specifically consider route economics, aircraft utilization, airport access, regulatory approvals, and the sustainability of its low-cost model.
Client specificity: Use the language, economics, constraints, and objective of the actual case.
This demonstrates that you are solving the client’s problem rather than reciting a memorized framework.
9.9 Prioritizing Within Your Structure
A structure should not imply that every branch deserves equal attention. Once you present the structure, identify where you would begin and explain why.
You might prioritize based on:
- Magnitude: Which area could have the greatest impact?
- Likelihood: Which explanation appears most plausible?
- Evidence: Which area can be tested quickly?
- Client context: Which issue appears most urgent or relevant?
Strong behavior: “I would begin with pricing because the prompt tells us volume has remained stable while revenue has declined.”
9.10 Connecting Every Branch to the Client’s Objective
Every major branch should help answer the client’s question. If you cannot explain why a category matters to the objective, it may not belong in the structure.
For a market-entry case, for example, “company culture” might be relevant only if it affects the organization’s ability to enter or operate successfully.
Discipline: Ask, “How will understanding this branch help me make the final recommendation?”
This keeps your structure focused and prevents unnecessary analysis.
9.11 What Interviewers Look for While You Structure
Interviewers are usually evaluating more than whether you mention familiar categories.
They look for whether your structure is:
- Logical: The categories make sense together.
- Relevant: The branches connect to the client’s objective.
- Complete enough: You have not missed an obvious major driver.
- Specific: The approach reflects the actual case.
- Prioritized: You know where you would start.
- Communicate clearly: The interviewer can follow your thinking.
The best structures show judgment, not just organization.
9.12 Common Structural Mistakes
Several mistakes appear repeatedly in case interviews.
- Using a memorized framework: The categories do not fit the specific problem.
- Creating overlapping branches: The same issues appear in several places.
- Missing a major driver: The structure cannot fully answer the question.
- Being too broad: Categories such as “market,” “company,” and “competition” are not developed enough to guide analysis.
- Overcomplicating the structure: Too many branches make prioritization difficult.
- Failing to prioritize: The candidate presents a structure but cannot say where to begin.
- Disconnecting from the objective: Interesting topics appear even though they will not affect the client’s decision.
Final principle: A good case structure is a working tool, not a performance. It should simplify the problem, identify the important questions, guide your next analysis, and keep every part of the case connected to the client’s objective.
