Expert with best answer


100% Recommendation Rate

21 Meetings

444 Q&A Upvotes

USD 239 / Coaching

Estimate the number of people since ever?

Rami asked on Apr 14, 2019
Please, if possible, no preplounge cases.

Estimate the number of people since ever?

2 answers

  • Upvotes
  • Date ascending
  • Date descending
Best Answer
updated his answer on Apr 17, 2019
BCG Consultant | MBA Stern | 100% interview success rate (8/8 incl BCG, A.T. Kearney, Strategy&) |Personalized interview prep
Book a coaching with Ian

100% Recommendation Rate

21 Meetings

444 Q&A Upvotes

USD 239 / Coaching

This is definitely a top-down (as opposed to bottom-up) sizing.First, I'll assume homo sapiens.

There's a lot of ways to approach this, but I would personally segment it by world population over time. I know that population growth is exponential, and I roughly know the population in different periods - however I have to be careful to account for "existence" i.e. birth/generations.

A lifespan is around 70, but I'll round down to 50 (which averages out across all of time).

  • I know there's about 7 billion people today.
  • Going back 50 years (1960s) there were around 4 billion.
  • 50 years again (1910s) that was around 2 billion
  • Now I'll keep that # but double the count to 100 years (in 1800s, 2 billion people). I.e. population was around a billion, but lets count it twice to account for births.
  • In 1700s, down to 1 billion (again, population of around 500 million?)
  • And I'll keep this 500 million x 7 down to the 1st millenium (3.5 billion).
  • Now, I'll drop it to mellenium, and keep 500 million down to when "civilization" emerged, around 4,000 BC. So, 500 million X 5 = 2.5 billion.
  • Then, we're into an extremely long tail for hundreds of thousands of years but very low population, so I'll throw in another 500 million.

If I were to draw this on a chart, it'd be exponential, so I'd a least be comfortable with that.

I'll add 7+4+2+2+3.5+2.5+.5 = 31 Billion people.

However, I know that, for most of history, death rates were absolutely horrid and that something like 50% of all people died before the age of 7. So, I'll multiply 31 billion by 1.5 to get the answer: 46.5 billion people have existed in the world.

Am I close?


very close. according to PRB the number is 108 billion. — Olzhas on Apr 25, 2019

When you are looking at current pop of 7B, and then counting up the population of 1960 of 4B, aren't you double counting the people within the 7B group that lived since 1960? — Anonymous on May 11, 2019

Serhat replied on Apr 25, 2019
BCG | Kellogg MBA |82% Success Rate| 350+ coachees | 5+ year consulting | 30+ projects in ~10 countries
Book a coaching with Serhat

100% Recommendation Rate

47 Meetings

521 Q&A Upvotes

USD 319 / Coaching

Hi Rami,

We are happy to provide you feedback on your solutions.

Would you want to try your best solution first? Happy to improve it together.



Related BootCamp article(s)

Important Facts

It's essential to know some key figures regarding geographies, population, economies for your case interviews. We summarized them for you here.

Market Sizing

Market Sizing Cases are used to test your quantitative and reasoning skills. The interviewer evaluates your structure, numbers-handling and business sense.

Interviewer-Led vs Candidate-Led cases

Case Interviews can be led by the candidate or by the interviewer: In Candidate-led cases the main challenge is the structure. In Interviewer-led cases the main challenge is to adapt quickly

Related case(s)

Your client, large automotive OEM WyCar, has developed its first fully electric vehicle (EV) and introduced it as a pilot on the Austrian market last year. However, sales have been far below the expected numbers. The management has engaged you to support them in understanding the reasons and advise ... Open whole case

Bain Case: Old Winery

Solved 28.7k times
4.4 5 777
| Rating: (4.4 / 5.0)

You have inherited the “Old Winery” from your grandfather, a winery which has been family owned for five generations and can be dated back to the 16th century. Half of the eleven hectares are used to grow white grapes, the other half to grow red grapes. They are grown in the conventional way, i.e. ... Open whole case

Roland Berger Case: Onlinestar

Solved 17.3k times
4.3 5 369
| Rating: (4.3 / 5.0)

Onlinestar, an online retailer of furniture and garden products (core business), has grown significantly in recent years as a result of an expansion of its product portfolio. The company mainly imports goods from Chinese manufacturers but also operates its own production of cat lavatories (special b ... Open whole case


Solved 48.1k times
4.5 5 1496
| Rating: (4.5 / 5.0) |

Nutripremium is a very well-known premium nutrition food company in Europe (€1 billion revenue last year). It is based in Spain and has an excellent market share not only in its home country but also in Portugal, France, Italy and Germany. Nutripremium has two main lines of products: Vitamin-supp ... Open whole case

Children vaccine

Solved 43.5k times
4.4 5 1444
| Rating: (4.4 / 5.0) |

Beyer, one of the biggest pharmaceutical companies in the world, just invented a very reliable vaccine against Chickenpox, a disease that affects children in the age from 2 to 16 years. Beyer came to you wondering what their potential sales in Europe in the first year would be if they launched this ... Open whole case