boys and girls The answer (assuming any particular kid is equally likely to be a boy or a girl) is surely exactly 1:1 - it doesn't matter who's having the babies, and what their reasons are for continuing to breed or not - that's just a red herring. Unless families are actually killing the girls, the number of boys and girls in the country will be the same number who were born, and there's no reason for any one particular baby to be more likely to come out male. So no maths is required to convince yourself that it's 1:1.
Chris Harris
Actually the proportion is 52:48. There are slightly more boys born than girls.
Stephen Jones
Yeah i thought that might be the case. Hence the assumption. But then it seems to me that the proportion will be the same whatever criterion the parents use to decide whether to have a baby (unless it involves some kind of genetic test/screening to check/affect the likelihood of them having a boy). Is this the case? E.g. say instead people only stopped having kids if and when they had twice as many boys as girls - what would the expected proportion be then? It seems less intuitive then but i reckon it'd still be 52.48% or whatever
Chris Harris
Yea, you're right. I was only being pedantic.
Stephen Jones
Slightly more boys are born than girls but boys have a higher mortality rate. So by the end of the first year the ratio is about even.
Jim Kennedy
I've actually heard in the past that Girls have a slightly higher birth rate due too the X chromosome sperm cell being slightly larger and more resilient then the Y chomosome, but its been some time since I have done any reading on the subject.
Kristian M. Pownall
x
I've heard that if intercourse occurs significantly before ovulation girls are more likely and as time goes it skews towards boys. The "speedy-y, hardy-x" theory was once popular but seems to have evidence which discredits it...
WanFactory
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