[["It is estimated that the world population reached one billion for the first time in 1804.", 679.0], ["It is estimated that the population of the world reached one billion for the first time in 1804. It would be another 123 years before it reached two billion in 1927, but it took only 33 years to rise by another billion people, reaching three billion in 1960.", 429.0]]
when did the world population reach one billion
history