Experts say that in 2007 the world population increased by 211,000 people every day. Did experts arrive at this figure by actually counting the...

I'm not sure once in how many years the census is
conducted in each country to determine the population. I guess it is around once every 5
years.

To arrive at the number by which the population of
the World is increasing everyday, experts don't have to count the number of people born
each day and subtract the number of people that die each day from it. That is something
that would be impossible to do.

A rough increase in the
World population everyday can be estimated using other methods. Experts can take the
latest population figure of each country and subtract from it the population figure
during the previous census. The increase in population can then be divided by the number
of days that have passed between the two census. This gives the increase in population
everyday for each country. The sum of this for all the countries would give a rough
estimate of how much the population of the World is increasing by
everyday.