A related question-
I seem to remember reading or hearing that the sex of a child after the
first is substantially more likely to match the sex of the previous child
than not. Does anyone have any information about this, or is it complete
nonsense?
Gordon Bushaw
Central Kitsap HS
Silverdale, WA
-----Original Message-----
From: Bob Hayden [mailto:[EMAIL PROTECTED]]
"Sex, of course, is one of the most readily observable components of
population structure. People may misrepresent their age, but they are
less likely to misstate their sex. The sex composition of a
population is conventionally expressed by a summarizing device called
the sex ratio, the masculinity ratio, or the ratio of males to
females.
"In the populations of most Western countries, including the United
States, the sex ratio at birth is about 105%... For American blacks the
sex ratio at birth is about 103%.
"More male than female births is a feature of most mammals..."
Then I have a preprint of a paper "Excess Female Mortality and the
Balance of the Sexes in the Population: An Estimate of the Number of
'Missing Females'" by Ansley J. Coale at Princeton.
"The masculinity ratio at birth has a limited range when calculated
from large numbers of births with accurate registration. For
aggregate births in 1962-1980 in 24 countries in Europe, the ratio
ranged from 1.05 to 1.07."
My recollection is that these differences are too large to be due to
chance, but no one knows their cause, nor why more males than females
are born. That pattern emerges in populaation records as far back as
such records have been kept.
_
| | Robert W. Hayden
| | Department of Mathematics
/ | Plymouth State College MSC#29
| | Plymouth, New Hampshire 03264 USA
| * | Rural Route 1, Box 10
/ | Ashland, NH 03217-9702
| ) (603) 968-9914 (home)
L_____/ [EMAIL PROTECTED]
fax (603) 535-2943 (work)
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