The population of the world was relatively low and steady until the 1950s when there was a population ‘explosion’. Since then, there has been a rapid increase in the world’s population so that in 2011 it passed 7 billion. The majority of this population growth is again in the developing world.
The reasons for this rapid expansion is mainly the decrease in global death rates while birth rates remained very high. This meant that many more people were being born than were dying so the population grew.