latest stories:    © / Julie Fairman  Every few years, public
officials and the news media perform a ritual form of
"disestimation" when a population clock reaches a big milestone.
Population experts at the Census Bureau and around the world are
constantly estimating the populations of each nation. Their
estimates are pretty good, predicting when, say, the world's
population reaches six billion—they might even be able to guess
when the six billionth person is born to within a few hours.
That's about as good as any possible measurement of population
can get. Populations constantly fluctuate, with people dying and
being born at irregular intervals, often far from the eyes of
people who count such things, so it's impossible to know at any
given moment the true number of people alive on earth.
Nevertheless, on October 13, 1999, as flashbulbs popped around
him, UN secretary-general Kofi Annan held a young Bosnian boy,
welcoming him into the world as the six billionth person on
earth. (The UN insisted that Annan's