The result was a veritable revolution in falling death rates and rising life expectancy in both the developed and the developing world. Plummeting death rates in many areas raised population growth rates to levels the world had never known before. Reference to a worldwide population explosion, unthinkable for most of human history, became commonplace in the 1960s and 1970s as the world’s population grew to 3 and then 4 billion. World population passed 5 billion in 1987, 6 billion in 1999, and 7 billion early this decade; almost all this growth has occurred in the developing countries. Between 1945 and 2009, the growth in world population averaged a historically unprecedented rate of 1.6 percent per annum, twenty times faster than the estimated 0.08 percent between 1 C.E. And 1800.