When did the population double

Things sped up considerably in the middle of the 20th century. The fastest doubling of the world population happened between 1950 and 1987: a doubling from 2.5 to 5 billion people in just 37 years — the population doubled within a little more than one generation.

Here is a picture  of the net. its 4 squares in a row diagonal and on the third draw one square aove and under