How long would it take a pay-it-forward chain to reach 7.4 billion people?


Originally published at:


The cynic in me needs to point out that this math also works to dissuade someone from joining a pyramid scheme. You realize quickly that there simply isn’t enough people in the world to give anyone but those near the very top all the benefits.

Really regretting eating that cynic whole, BTW. The indigestion is killing me.


Agreed. I’m going to tell three people, and have them each tell three people, and so forth. Although to incentivize everyone, let’s make it so that everyone gives the person above them $10 and 10% of the money that people below them sent. And as much as I hate to prey on people’s superstitions, it’s really important that people learn about pyramid schemes, so I’m going to put in something about there being a curse on anyone who doesn’t forward it on.


This of course assumes that everyone will actually pay it forward and that there are no repeats ie that only those who have not been paid forward are the recipients.


I was thinking this. It’s not like the people who have received the benefit previously would be somehow visually marked, also it becomes a logistical nightmare to track down people that haven’t been paid forward even among densely populated areas.


There’s different kinds, this might have been an ar-cynic.

(Ar, ar, ar!) :)


The repeats issue is brought up in a somewhat dismissive popup comment at about 2:50.


Hi! I made this video and this is a very valid point. I hoped that this would not take away from the fact that the acts can still spread quickly even with repeats, I’m sure calculating the probability of repeats in a certain area would be pretty complicated.

It also assumes that no layer will advance until everyone in the previous layer has connected with their 3 people, which is also highly unlikely.


To make the benefits spread maximally fast, we’d need a way to prevent redundant rewards being paid to the same person. Like a card you hold up when someone starts doing something abjectly nice for you for seemingly no reason, that says, “Thanks, I’ve already been paid-it-forwarded” (or whatever the past tense of that phrase is).


I don’t see this assumption. Making that assumption would make the probabilistic calculations easier, but the problem should still be solvable otherwise.


Thanks for making the video. It is interesting how quickly it spreads. Rather like the 6 degrees of separation.


I have been both a recipient and a giver of pay it forwards. I have even recently paid forward a kindness I received this year. You know who you are.

I have usually paid forward the kindnesses I have received multiple times over because of the impact that the loving act has had on me. At least two acts of kindness came at such crucial, hard times in my life. Not all at once, but over the years, I have thought of them and tried to act on that kindness. I’m not sure how the record keeping of it all goes. Pretty sure I’m in the red.

Maybe I’m a weirdo. You gotta factor in us weirdos who not only pay it forward, but then over and over again keep paying forward.


I would like to apologize to @problemsolverchannel for how i’ve approached this and especially for characterizing your acknowledgment of the repeat issue in the video as “dismissive”. In truth this is a rather nice demonstration of geometric sequences and series.


Over the course of my life at the seemingly lowest points i’ve had to go through i was helped out immensely by people i hardly knew. Every time. It’s saved me from myself and from the circumstances i found myself in and those acts of kindness are moments i can never ever repay. The only way to even begin is to pay it forward ad-nauseum any chance i have, which i do.


I meant to reply, but no i don’t think it takes away from the message you were trying to convey. I was just sharing the initial thoughts i had on the practicality of it. It’s obviously worthwhile being kind to as many people as you can, even if they’ve already been helped previously. Thank you for taking the time to hop on here to discuss with us :slight_smile:


No worries! It’s definitely an issue that is worth recognizing and one that I could have addressed more explicitly in the video.


Awesome, I’m glad the message still worked! I’m just grateful to see my videos shared and discussed!


This is kind of similar to the ‘X degrees of separation’ concept. Last year, Facebook claimed that you are only 3.57 degrees separated from everyone else on Facebook, if you were actually on Facebook, which you aren’t because you’re all way too cool for that.


You’ve got it all backwards. $10 and 10% is thirteen dollars. The curse is on you.


Isn’t this similar maths to a nuclear chain reaction…3 neutrons per collision…