Schedule mock interviews on the Meeting Board, join the latest community discussions in our Consulting Q&A and find like-minded Case Partners to connect and practice with!
Back to overview

Estimate the number of people since ever?

Estimate the number of people since ever?

2 Answers
2.9k Views
4
Be the first to answer!
Nobody has responded to this question yet.
Top answer
Ian
Coach
on Apr 17, 2019
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

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?

on Apr 25, 2019
very close. according to PRB the number is 108 billion. https://www.prb.org/howmanypeoplehaveeverlivedonearth/
on May 11, 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?
Serhat
Coach
on Apr 25, 2019
BCG | Kellogg MBA |82% Success rate| 450+ case interview| 5+ year consulting | 30+ projects in ~10 countries

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.

Best

Serhat

Similar Questions
Consulting
Best Preparation Method for Written Cases at Bain and BCG?
on Nov 02, 2015
Global
4 Answers
20.8k Views
Top answer by
69
4 Answers
20.8k Views
+1
Consulting
Is it difficult to join McKinsey BCG or Bain as an experienced professional?
on Nov 10, 2023
Global
18 Answers
109.6k Views
Top answer by
119
18 Answers
109.6k Views
+15
Consulting
Einstieg bei einer Top-Beratung (McKinsey, BCG, Bain, Roland Berger)
on Nov 11, 2015
Global
1 Answer
14.2k Views
Top answer by
58
1 Answer
14.2k Views
How likely are you to recommend us to a friend or fellow student?
0 = Not likely
10 = Very likely
You are a true consultant! Thank you for consulting us on how to make PrepLounge even better!