BCG Market Sizing Case 2027: Framework & Worked Example

For the BCG market sizing case — commonly reported by candidates as "How would you estimate the market size for electric scooters in London?" — use this framework: define the market, segment the population, estimate penetration with stated assumptions, sanity-check the result. The interviewer grades your structure and math, not the final number.

What This BCG Market Sizing Case Assesses

Market sizing tests structured thinking under ambiguity. There is no right answer — the interviewer watches how you break a fuzzy question into clean parts, make reasonable assumptions explicit, and do quick mental math without errors. It's commonly reported by candidates as a warm-up that sets the tone for the rest of the case.

How to Answer This BCG Market Sizing Case

Walk through these steps, stating each assumption aloud:

• Define the market. Clarify scope first: annual revenue from electric scooter sales in London (new units only, not rentals) or annual market value — pick one and commit.
• Segment top-down. London's population is roughly 9 million. Estimate the relevant buyer pool: working-age adults commuting, say 40%, which gives about 3.6 million. Then estimate penetration: perhaps 2% own an e-scooter, giving 72,000 owners.
• Convert to value. Assume an average scooter price of £500 and a replacement cycle of 3 years, so roughly 24,000 units bought per year, or about £12 million in annual sales.
• Sanity-check. Compare against a known reference — e.g., bicycle sales in London — and adjust if your number looks absurd. Saying "this feels low/high because..." shows judgment the interviewer wants to see.

Note: these figures are illustrative assumptions for the exercise; the exact numbers will vary, and the method matters far more than precision.

Common Mistakes

• Skipping the clarification. Jumping straight to math without defining the market is the fastest way to solve the wrong problem.
• Hiding assumptions. Assumptions you never state can't earn credit — narrate every number you introduce.
• Arithmetic errors. Round aggressively (9M → 9, 2.1% → 2%) so the math stays clean; exactness is not the point.

Candidates commonly report that the market sizing question decides the interviewer's first impression of their structure. Because the numbers are yours to choose, there is no excuse for a disorganized approach — rehearse two or three sizing drills so the framework is automatic.

Keep Reading

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• BCG Market Sizing Questions: Framework & Worked Examples

FAQ

Does the final number matter? No. Interviewers grade the structure, the stated assumptions, and the math. A well-reasoned £12 million and a well-reasoned £30 million can both score full marks.

Top-down or bottom-up? Use whichever is cleaner for the question, but top-down (population → segment → penetration) is usually faster and easier to narrate.

What if my sanity check says the number is wrong? Say so and adjust. Catching your own error aloud is a positive signal, not a failure.

Should I ask the interviewer for data? Only for clarifying scope. In sizing, you're expected to supply the assumptions — asking for every number signals you don't understand the exercise.

Preparing for BCG's interview? Our 2027 BCG Consulting Career Assessment, Online Case and Quantitative Reasoning Test Tutorials has practice questions and answers — $79 one-time, instant download.