From year 1 on our calendar to the beginning of the Industrial Revolution around
1750, it tripled to 728 million people, less than three-quarters of the total number
living in India today. During the next 200 years (1750–1950), an additional
1.7 billion people were added to the planet’s numbers. But in just four decades
thereafter (1950–1990), the earth’s human population more than doubled again,
bringing the total figure to around 5.3 billion. The world entered the twentyfirst
century with over 6 billion people. Figure 6.1 shows how rapidly total
population grew after 1950 in comparison with the two centuries before that. It
vividly portrays the magnitude of population growth, most of which has been
in developing countries, both as a percentage of the total and in terms of absolute
numbers. Finally, it provides projections to 2050, when world population
is expected to reach 9.2 billion.