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Possessing general knowledge is indispensable especially for market sizing cases

In a case interview, you must be familiar with basic data about geographies, population, life expectancy, and economies especially for the country you are interviewing for and popular countries such as the US where most big consulting firms are based. Having this knowledge demonstrates that you are well-read and have a potential to be business savvy. Thus, besides being able to solve highly complicated algebraic problems, you should know basic information such as population of your home country and of some key countries of the world. Obviously, it would be embarassing to not know the population of the country you live in especially if your client notices this!

Most importantly, you will likely need this information for most market sizing cases and backing assumptions with known facts such as population data makes the entire exercise of estimation much more plausible and reliable. Having knowledge of such figures can also be beneficial for sanity checks at the end.

Here are some basic facts we pulled together for you (ideally you should memorize these or at least have an idea of the "order" if not exact numbers):

World total 7 b
China 1,3 b
India 1,2 b
Europe 500m
USA 320m
Indonesia 250m
Brasil 200m
Russia 140m
Japan 130m
Germany 80m
UK 64m


Days / year 365 d
Days / 3 years 1000 d
Weeks / year 50 w
Hours / week 168 h
Seconds / hour 3600 s

Country/Region GDP (Millions of $US)
World 72,689,734
1 United States 16,244,600
2 China 8,358,400
3 Japan 5,960,180
4 Germany 3,425,956
5 France 2,611,221
6 United Kingdom 2,417,600
7 Brazil 2,254,109
8 Russia 2,029,812
9 Italy 2,013,392
10 India 1,875,213

(Source: Wikipedia)

Fractions Percent Decimal
1/5 20% 0,200
1/6 17% 0,167
1/7 14% 0,143
1/8 13% 0,125
1/9 11% 0,111
1/10 10% 0,100
1/11 9% 0,091
1/12 8% 0,083
1/13 8% 0,077
1/14 7% 0,071
1/15 7% 0,067
1/16 6% 0,063
1/17 6% 0,059
1/18 6% 0,056
1/19 5% 0,053
1/20 5% 0,050
9 Comment(s)
February 24, 2015 07:49 pm -

Thanks everyone for their comments. As a general rule of thumb - make sure to know facts such as population, life expectancy, household size etc. on an average for the country you are interviewing for and popular countries such as the US where most consulting firms are based. We have not included information for many countries because there would be too many to list :)

February 23, 2015 03:08 pm -

I would add few other things that might be useful for market sizing:

- Life expectancy 80 years (US) 70 years (World)
- 4 mln people per age group
- >100 mln U.S. households
- 200 mln households in Europe

June 04, 2014 01:21 am -

Turkey Population: 75 million(round up to 80 million for calculation sake) :))

May 22, 2014 05:05 am -
Luis Miguel

this page provides a good comparison on economic data.

April 24, 2014 07:30 pm -

I don't think they just gonna ask you those numbers. But it's useful for communication and calculations to know what fractions are in percentages. It's way easer to talk about 6% of something or calculate 6% of something instead of using 1/17.

April 24, 2014 07:14 pm -

How are these going to be used during the interview process?

March 05, 2014 04:38 pm -

To generally evaluate markets I'd use growth rates. They also come in handy as I can compare them with company specific growth rates to see if a company performs good/bad. For industrialized G8 or G20 countries I'd assume an average of 2%

March 05, 2014 04:28 pm -

Often needed: Expected life span (80 years) and average number of children per woman (2)

February 26, 2014 06:24 pm -

Thx for the overview.! Maybe add GDP Europe: $17,228,000 Mil and GDP Eurozone: $12,752,000 Mil (2013, Wikipedia:

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