Your place among 7 billion people

It's a numbers game, to be sure, as humanity reaches a milestone of 7 billion people living on Earth.

The United Nations Population Division, using its best estimates, has designated Oct. 31, 2011, as a symbolic date when a baby born somewhere will push humankind into new territory. That has rekindled a ferocious debate among anti-abortion activists who love to imply that choosing Halloween to mark the occasion is just another left-wing scare tactic and those concerned about women's rights, reproductive health and a burgeoning numbers of consumers living within their means on a finite planet.

Enter Population Action International, which has come up with a clever way to help you find your spot on the growth curve. Key in your birth date, and PAI's mathematical formula, using U.N. data, will estimate your number as a way to illustrate how much the global population has grown since you were born. Fair warning: PAI has struggled to keep up with demand on its website. That's not altogether surprising, given how many of us there are, with an estimated 227,252 added every day.

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-- Kenneth R. Weiss

Image: Population Action International's interactive website