On October 31, 2011, the United Nations and a number of governments marked the day on which the world population was estimated to reach seven billion, and ceremonies were held in several countries where a child born on the day was presented as the symbol of the milestone. The date was a convention rather than an exact measurement, since the total is an estimate based on census returns and on birth and death records, and the count is always a few months or years out. The numbers rose fast. The figure had passed six billion in 1999 and five billion in 1987.
The growth was uneven. Most of the increase was taking place in Asia and in Africa, and the largest single contributor was India, which was expected to pass China as the most populous country within a few years, and the highest rates of growth were in the countries south of the Sahara, where families were larger and health care and schooling lagged behind. In much of Europe and in Japan the population was stable or falling, and many countries in those regions were trying to attract immigrants to fill the gaps in their labour forces.
The reasons behind the numbers were studied closely. Death rates had fallen sharply through the twentieth century with better medicine, clean water and food supply, and birth rates had fallen too, but more slowly, and the result was a period of rapid growth that was expected to end in the middle of the present century, when the total is expected to level off at about ten billion. The trend is slowing. The decline in birth rates has been linked to education for girls, to the availability of contraception and to the movement of people into cities, where large families are less useful and more expensive.
The milestone was discussed in terms of both strain and progress. More people meant more demand for food, water and energy, and questions about whether the land and the climate could support them, and it also meant that more people than ever were living longer and better than their grandparents, and that the share of the very poor had fallen. The United Nations used the day to press for family planning and for schooling, and the subject of population policy has stayed in the centre of the debate about development and the environment. The debate goes on.