I feel like maybe all it takes for a site like Manifold to appeal to you is for you to think you're smarter than average and will make better bets (whether or not this is true). And maybe those with only younger siblings come out of childhood thinking they're smart because the main kids they interact with at home have been alive for fewer years.

First borns without siblings and first borns with siblings were different entries. So actually first borns are LESS numerous in this case, because families with only one child don't count and families with 3+ children count double or triple or more

@Tumbles There are still more firstborns than thirdborns in this scenario

@Tripping That's true, but the poll has firstborns with siblings far outnumbering all other options put together!

@Tumbles And one of the reasons is that there are more firstborns

@Tripping yeah I agree it's not a bad point, more firstborns than thirdborns isn't the surprise, but it is surprising that within multisibling families the polls find more firstborns than secondborns no?

@Bayesian like just to make sure i understand your point right, it shouldn't justify that trend, only the 1st > 3rd and 1st > 4th and so on?

@Tripping There are more human beings that are 2nd sibling or more in the world than there are firstborns with siblings

Edit: ah I suppose it still makes sense to answer the general question of "why does the poll look this way". The point isn't trying to answer "why do firstborns with siblings outnumber all others put together"

could that be false if there were a sufficient amount of twins that don't count as second siblings

don't think this is more right than the other option but is an effect worth considering

@Bayesian ooo good one! They definitely grow up with less experienced parents on average, pretty much by definition. At the very least it's always something to consider when you are looking at peaks but not valleys