PrepLounge - link to homepage PrepLounge - link to homepage
Consulting Consulting
Consulting Finance General
Login Sign up for free Sign up for free
Consulting Finance General
Community
Meeting Board
Consulting Q&A
Interview Partner
Premium Membership
Coaching
Coaches
Coaching Packages
Consulting Q&A
Resources
Case Interview Basics
Case Library
AI Casebot
Tests & Guides
Mental Math Tool
Stress Questions
Drills
Video Tutorials
Brainteaser
Career
Employers
Career Events
Consulting Jobs
Consulting Blog
Sign up for free
Login
Community
Meeting Board
Consulting Q&A
Interview Partner
Premium Membership
Coaching
Coaches
Coaching Packages
Consulting Q&A
Resources
Case Interview Basics
Case Library
AI Casebot
Tests & Guides
Mental Math Tool
Stress Questions
Drills
Video Tutorials
Brainteaser
Career
Employers
Career Events
Consulting Jobs
Consulting Blog
Schedule mock interviews on the Meeting Board, join the latest community discussions in our Consulting Q&A and find like-minded Interview Partners to connect and practice with!
Meeting Board
Consulting Q&A
Interview Partner
Premium Membership
Back to overview
Javier
on Oct 09, 2018
Global
I want to receive updates regarding this question via email.

Market Sizing Doubt

Hi, I would value anyone's point of view about this market sizing question. Just so you do not get shocked on how useless I am, I have no Case Interview experience whatsoever;) I work at an international bank within the M&A division, and never got asked these when going through recruiting (luckily for me)

So the other day I was asked, during an interview with a Fintech, to calculate the number of coins that are thrown each year to the Trevi Fountain (in Rome). 

So I think the easiest way possible (it seems my answer was far from being right since I was rejected;))---> number of annual tourist x coins per tourist + number of romans x coins per roman

I segmented the number of tourists by season (assuming summer brings more tourists) and made up the numbers for each season.

To calculate the number of thrown coins per tourist/roman I divided between high income, medium income and low income, assuming tourists had a higher proportion of high income people.

Again, I completely made up the number of coins per each income segment.

The outcome of the interview, even though my interviewer told me the reasoning was ok, was me being rejected...

I don't really care that much about that specific interview since that company didn't attracted me so much, but I realle need to know how you guys would have solved that question if given the chance.

As I said, any comment, point of view, help would be more than appreciated, really.

Thank you in advance,

Javier

The other day I was asked during an int

4
2.9k
12
Write an answer
Be the first to answer!
Nobody has responded to this question yet.
Top answer
Deleted user
on Oct 09, 2018

Hi Javier!

I do see where your reasoning comes from - personally I would've segmented the coin-throwers differently. The segmentation of tourist and Roman makes sense, as the two categories would certainly impact the number of coins thrown in per year. However I'm not sure income would necessarily impact the number of coins thrown - actually, it may even be the opposite correlation from what you expect, as lower income people tend to be more superstitious.

I guess the key here would be identifying a broader market size and narrowing down with relevant. You could even make an educated guess that realistically only tourists will significantly impact the number of coins tossed into the fountain.

E.g. Annual visitors to Rome*proportion visiting Fountain Trevi*proportion throwing coins into fountain*average number of coins per throw

I would say your approach perhaps missed a few steps e.g. do all tourists in Rome visit the fountain? Does every tourist toss a coin in? Do locals actually toss coins in?

The key to market sizing is a balance of real-world sense and sound logical reasoning. Although I can follow your steps, I don't think the segments you produced were the best ones to use.

I hope that helps!

Kay

4
0 comments
Benjamin
Coach
on Oct 10, 2018
ex-Manager - Natural and challenging teacher - Taylor case solving, no framework

Hi,
I would proceed a bit differently, skipping the sgementation per income and introducting the tourist group size and coin / group instread (assuming in a family for instance, not everyone is throwing a coin..?)

# tourists visiting / Average tourist group size X average amount thrown for a group

Keep in mind that there is no unique solution for market sizing so yours would be valuable as well, and you might have been rejected for other reasons than the market sizing inself, unless it was more a behavioural concern during the sizing.

BEst
Benjamin

1
Contact coach
1 comment
Deleted user
Coach
on Oct 13, 2018
You obviously don't have kids :-) If you throw a coin, MOST DEFINITELY your children will want to throw one as well. And you're asking for drama if oyu only let one kid throw a coin, but the others not... :-D
Javier
on Nov 13, 2018

Hi, sorry for the delay!! I read your answers weeks ago and found them really insightful and helpful but have had some issues logging through my office's computer. It surprises me how everyone in this website is so nice and keen to help. Again, thank you both, Kay and Benjamin Best regards!!!

0
0 comments
Ian
Coach
on Dec 31, 2021
Top US BCG / MBB Coach - 5,000 sessions |Tech, Platinion, Big 4 | 9/9 personal interviews passed | 95% candidate success

Hi there,

Providing some market sizing thinking for anyone revisiting this Q&A:

Remember that there's rarely a "best" answer with market sizing. What's important is that you break down the problem the way it makes sense to you. Importantly, break it down so that the assumptions you make are the ones you're most comfortable in.

For example, do you know all the major brands? Great go with that. Do you understand all the segments of that country's population (either age or wealth or job breakdown)? Go with that. Do you know the total market size of the tourism (or hotel) industry? Then break it down that way.

Some tips:

  1. Just like in a case, make sure you understand the question - what are you really being asked to calculate
  2. Decide whether a top-down or bottom-up approach is best
  3. Figure out what you know you know, and what you know you don't know, but could estimate
    1. This helps you determine how to split out buckets
  4. Stay flexible - you can start with a "high-level" market sizing, but gauge your interviewers reaction....if it looks like they want you to do more...then go along level deeper in terms of your splits
0
Contact coach
0 comments
Sign up for free to read all answers.
Sign up for free to read all answers.
Yes, I would like to be informed about new content, exciting jobs, relevant events, and selected employers.
By creating an account, I confirm that I agree to PrepLounge's Terms of Use. Please read our Privacy Policy.
Sign up with
You already have an account? Log in here.
Similar Questions
Consulting
Guesstimate question - number of airplanes in the sky
on Aug 20, 2024
Global
4
2.2k
Top answer by
Hagen
Coach
#1 recommended coach | >95% success rate | 9+ years consulting, interviewing and coaching experience
56
4 Answers
2.2k Views
+1
Consulting
How to estimate the market size of the European bicycle market?
on Nov 28, 2024
Global
5
1.3k
Top answer by
Maria
Coach
Ex-McKinsey Engagement Manager in NYC | Part of the McKinsey Private Equity Practice
37
5 Answers
1.3k Views
+2
Consulting
Help - Market Sizing is always off by a 2-3 multiple
on Jun 05, 2025
Global
8
200+
Top answer by
Hagen
Coach
#1 recommended coach | >95% success rate | 9+ years consulting, interviewing and coaching experience
15
8 Answers
200+ Views
+5
Related Article
Market Sizing
Questions about market size are frequently asked in case interviews in consulting because they require a blend of logic, mathematics, and common sense. They can be asked as standalone questions or as part of a larger case. Applicants who are familiar with market sizing questions can really perform here. What Are Market Sizing Cases?If you're applying to top consulting firms like McKinsey, BCG, or Bain, you're unlikely to escape a market estimation case. Market sizing cases are considered "back-of-the-envelope" calculations because they can be done on the back of an envelope. Despite the name, it's not just about estimating market sizes; other estimations may also be asked for.For example, if you're discussing a British clothing retailer's growth strategy, you could calculate on an envelope how large the online clothing market is and what percentage of the market the retailer already penetrates. If you perform these calculations quickly, the conversation with the client stays fluid, leaving a good impression.You can receive the question about market size as a standalone case (although this is less common) or as part of a more comprehensive problem, such as market entry. The good news: There's no right or wrong answer when it comes to the question of market size. The interviewer is less concerned about the specific number you come up with for the market than the approach you took to arrive at that number. Why Are Market Sizing Cases Commonly Used in Consulting Interviews?Market Sizing Cases are used to test your quantitative and logical abilities. The interviewer wants to ascertain whether you work well with numbers and if you can make informed assumptions and deal with ambiguities. Questions about market size aren't just about the size of markets; they also involve other types of estimations, such as the number of golf balls in a jumbo jet. As you may have noticed, math is crucial in tackling these questions since you don't have a calculator to rely on. Most importantly, you need to be comfortable dealing with large numbers like millions and billions as well as percentages. More on that later. How Do You Best Approach Market Sizing Cases?Now that we understand the theory behind Market Sizing Cases and their relevance to your case interview, let's take a closer look at the process.Segmentation – The Key to Market Sizing CasesIf you've done some reading on case interviews before delving into market sizing questions, you might have come across areas where segmentation is necessary. Segmenting data is a crucial skill you must master as both a candidate in a case interview and in your later career as a consultant. Segmentation generally refers to dividing a larger whole into smaller parts or segments. The principle you need to understand to do this correctly is the MECE principle.MECE stands for "mutually exclusive, collectively exhaustive." Simply put, segmenting a group of data according to the MECE principle means forming subgroups that do not overlap but collectively cover the entirety of the data, meaning no data is missing. An example useful for market sizing questions is dividing a country's population into age groups (as different age groups often behave differently).Below is a breakdown into Group 1 in the age range 0 to 14, Group 2 in the age range 15 to 64, and Group 3 for everyone over 65: Note that none of the groups overlap, so no age is counted twice, but also no age is overlooked. Now that the population is correctly segmented, we can treat each group differently. If we had divided the population of the United Kingdom into the aforementioned groups, we could estimate clothing expenditures per person in these groups in online retail. Common sense suggests that expenditures per person in the 0-14 age group are lower than in the 15-64 age group. We can justify this estimation by noting that the majority of 0-14-year-olds do not purchase their clothing online. 
View article
Related Case
Company case by
RWE Consulting
RWE Consulting Case: Floating Wind in Japan
5.0
28.3k times solved
Intermediate
Interviewer-led
Open case
Similar Questions
Consulting
Guesstimate question - number of airplanes in the sky
on Aug 20, 2024
56
4
2.2k
Consulting
How to estimate the market size of the European bicycle market?
on Nov 28, 2024
37
5
1.3k
Consulting
Help - Market Sizing is always off by a 2-3 multiple
on Jun 05, 2025
15
8
200+
Everything for Your Career
  • Interview Coaching
  • Q&A
  • Interview Partner
  • Mental Math Tool
  • Interview Drills
  • Stress Questions
  • Blog
Everything for Your Career
  • Interview Coaching
  • Q&A
  • Interview Partner
  • Mental Math Tool
  • Interview Drills
  • Stress Questions
  • Blog
Popular in Consulting
  • Case Library
  • Meeting Board
  • Interview Partner
  • Case Interview Basics
  • Case Interview
  • Consulting Q&A
Popular in Finance
  • Finance Q&A
  • Interview in Investment Banking
  • Investment Banking Salaries
Popular in Consulting
  • Case Library
  • Meeting Board
  • Interview Partner
  • Case Interview Basics
  • Case Interview
  • Consulting Q&A
Popular in Finance
  • Finance Q&A
  • Interview in Investment Banking
  • Investment Banking Salaries
Consulting and Finance Employers
  • RWE Consulting
  • Whiteshield Advisory
  • All Employers »
About PrepLounge
  • For Companies
  • For Universities
  • For Coaches
  • About Us
  • Career
  • FAQ
© 2012 PrepLounge
Our servers are powered by electricity from renewable sources.
  • Cookies & Privacy
  • Terms & Conditions
  • Imprint
  • Sitemap
  • Contact
Facebook Linkedin Instagram TikTok Youtube
Questions or Feedback?
Select category
  • Select category
  • General Feedback
  • Case Interview Preparation
  • Coaching
  • Technical Problems
  • Other
Your name
Your email address
Cancel