USA, October 31, 2011 (NYT) Feeling claustrophobic? You’re not alone. According to United Nations demographers, 6,999,999,999 other Earthlings potentially felt the same way on Monday when the world’s population topped seven billion. But if you’d rather go by the United States Census Bureau’s projections, you’ve got some breathing room. The bureau estimates that even with the world’s population increasing by 215,120 a day, it won’t reach seven billion for more than four months.
How do the dueling demographic experts reconcile a difference, as of Monday, of 28 million, which is more than all the people in Saudi Arabia?
They don’t.
“No one can know the exact number of people on the globe,” Gerhard Heilig, chief of the population estimates and projections section of the United Nations Population Division, acknowledges. Even the best individual government censuses have a margin of error of at least 1 percent, he said. Monday’s seven billion estimate actually may be 56 million off.
The US Census Bureau’s global population clock gives the pretense of greater precision. It projects that about 255 people are born every minute (about 367,000 a day) while about 106 die (roughly 153,000 a day). At that rate, the world’s natural increase would be about 78.5 million a year, or well more than the entire population of France, Britain or Thailand.
“Realistically, the uncertainty is at least 2 percent and that’s for the 75 percent of the world for which we have recent official counts or estimates,” Joel E. Cohen, head of the Laboratory of Populations at Rockefeller University and Columbia University, said Monday.
Dr. Goodkind of the US Census Bureau said the bureau revises its projections on a continuing basis, while the United Nations makes revisions every two years. Even so, the Census Bureau projects that the world population will hit seven billion next March 12 — well within the United Nations’ six-month, 1 percent window of uncertainty. So who’s right? “We’re not exactly in synch, but we’re pretty close,” Dr. Goodkind said.