In an idle moment just before Christmas I gave in to my obsession with population growth and checked a few of the world population clocks.

These are neat web enabled algorithms that calculate and display an estimate of the number of people in the world. They tick or scroll along in real time as they make a virtual count of the births and deaths of people around the planet.

At 10.30am Sydney time on the 21 December 2011 a sample of them read

• 6,880,986,220 on Poodwaddle
• 6,933,668,504 on Metapath
• 6,940,632,100 on Tranquileye
• 6,982,567,212 on US Census Bureau
• 7,010,439,251 on Worldometers

Clearly the algorithms and the underlying data sources produce some variability in the numbers.

Chances are that the true number is somewhere between 6,906,205,940 and 6,993,111,375 which is the 95% confidence interval for this sample of five estimates.

This confidence interval is 87 million roughly the population of Italy and Poland combined suggesting to the cynic that these clocks are not that precise.

Moving forward 101 days to 1 April 2012 and at 9.30 in the morning Sydney time the population clocks said

• 6,854,561,707 on Poodwaddle up  26,424,513
• 6,953,660,825 on Metapath up 19,992,321
• 6,962,506,474 on Tranquileye up 21,874,374
• 7,004,421,653 on US Census Bureau up 21,854,441
• 7,031,948,549 on Worldometers up 21,509,298

This is an average increase of 22,330,989 new people in the world in just 101 days.

That is 221,098 per day or, if you prefer, 9,212 per hour.

I use to say it was 8,000 an hour, maybe I should now say 9,000 although what is another 1,000 between friends?

And yes, there is some uncertainty. It may be only 7,000 per hour. Or it may be the upper end of 11,000. Either way it is a sizable village every hour and a small city each and every day.  Scary.

Read more in my Hubpage article, What do population clocks tell us?