Beginning with a world population of two billion in 1930, we will reach seven billion sometime late in 2011 (amounting to FIVE billion additional people in a single human lifetime), followed by still more billions (numbers eight and nine) on-track to arrive by 2041 and by the arrival of a tenth billion by century's end (or, if worldwide fertility averages just 1/2 child per woman higher, more than Fifteen billion by 2100).