The world reached a worrying demographic milestone. The US Census Bureau said the population passed 8 billion in September. However, it said this was a rough guess. The exact time could be a month or two earlier. The world population will continue to grow steadily. It grew from 6 billion to 8 billion in the past two decades. The population doubled between 1960 and 2000. The rate of growth is slowing because of falling birth rates.

The slowdown in population growth is due to lower fertility rates. The Bureau said the population would be 10.2 billion in 2060. It said: "Population growth in the future will come from larger groups of people at adult ages." It added: "Population growth is the result of fertility, mortality and migration.…[Most] of the earth's population reside in countries where fertility is around or below the replacement level."