Are there roughly 6,000,000,000/365 (16,438,356) people in the world
that share the same birthday, each day? Or is there a larger
sociological influence at hand, such as, more people tend to have sex
at time X, so more people are born at time Y, or so forth?

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Clarification of Question by idledebonair-ga on 24 Sep 2005 03:56 PDT

"disbursement," I mean...

Idledebonair --

This is an interesting one, as it's tough to find precise terms for a
good search strategy.  Here's one Google search strategy that seems to
produce good results:
"daily birth" statistics

The BBC says, "Long dark winter nights result in a high number of
summer births, according to new statistics. There is also a peak in
September, nine months after Christmas conceptions."

But you have to look out for 2 things:
1.  as the BBC article notes, with Caesarean or induced labor births
the date isn't so much related to date of conception but whether or
not the obstetrician is working weekends.
2.  There's a common belief that major events lead to increases in the
birth rate.  Indeed, the BBC story attributes that belief to a
midwife.  One of the great living urban legends is that after the New
York City blackout (1966), births increased dramatically.  The NY
Times had a role in perpetuating this myth, which statisticians have
debunked:

Snopes.com
http://www.snopes.com/pregnant/blackout.htm

I'll be interested to see what other researchers and commenters turn up.

Best regards,

Omnivorous-GA

Yes, isn't it a difficult one? I consider myself to be fairly crafty
at finding search terms but this one has me stumped. It started as a
conversation about why my friend knew so many people with September
birthdays(!), but I had reasoned that considering the sheer amount of
the people and that there are many people that do not celebrate
Christmas (the Chinese come to mind) that statistics must take over.
One idea was maybe it was linked to the temperature outside but we
thought that the two hemispheres would balance that out. We thought,
however, that maybe if people were more likely to copulate during the
Spring, for example, there would be two peaks during the year, one for
each hemisphere. I am still researching but have yet to find
conclusive evidence.

There is also the urban legend  -or fact -  that nine months after
9/11 there was a surge of births in USA and the explanation that in
times of crisis, people feel the urge to propagate.  There is a
similar one about more males being born during wars.
Northern vs southern hemisphere:  There are way more people in the
north, so that won't balance out.
Caesarean births should only make a couple of days difference.
Xmas:  in Germany, where carnival (mardi gras) is celebrated in some
regions with some excesses, it is joked that there is a surge in
winter births  - and more jokes about the possible fathers.
And then there are theories about the best time for kids to be born to
survive, if nature (Darwin's theory) has any effect.  Should that be
in summer, a less strenuous climate for a suckling infant?  Fits well
with those first cool autumn evenings.  Or should the pregnant mother
not have to eat for two in the winter and early spring when food was
sparse?
My kids:  one in summer vacation, the other, after New Year's eve.  :)

Believe you mean "distribution" (spread), not "disbursement" (payout).

In 1978, in the US, at least, the distribution was decidedly not even,
ranging from a bit more than 7,000 births per day, to a bit less than
11,000.  And as one of the comments already noted, peak births were in
September:

http://math.hope.edu/swanson/statlabs/proj1_sample.html

Maternity nurses report the same thing.  It's anecdotal only, but
there's something to it:  their busiest period of the year is
September.  "Those holiday parties!" says one, rolling her eyes.

Archae0pteryx