Permanent link to this comic: http://xkcd.com/605/
My friend Jerry* actually used to do this kind of extrapolation. In 2002, He extrapolated that by now I would have 57 grandchildren.
He only missed by 46.**
* RIP, and sorely missed. Damn, he could play some great jazz. Now I'm sad.
** If you think I have 103 grandchildren you have had either too many or too few martinis. Drink up and recalculate.