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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?

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Ian
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updated his answer on Apr 17, 2019
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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?

(edited)

very close. according to PRB the number is 108 billion. https://www.prb.org/howmanypeoplehaveeverlivedonearth/ — 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
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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

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