World Population Day is an annual event, observed on July 11, which seeks to raise awareness of global population issues. The event was established by the Governing Council of the United Nations Development Programme in 1989. It was inspired by the public interest in Five Billion Day on July 11, 1987, approximately the date on which the world’s population reached five billion people.
The world population on the 20th anniversary of Five Billion Day, July 11, 2007, was estimated to have been 6,727,551,263.
The term world population commonly refers to the total number of living humans on Earth at a given time. As of 11 July 2009 (UTC), the Earth’s population is estimated by the United States Census Bureau to be 6.77 billion.The world population has been growing continuously since the end of the Black Death around 1400.There were also short term falls at other times due to plague, for example in the mid 17th century.The fastest rates of world population growth (above 1.8%) were seen briefly during the 1950s then for a longer period during the 1960s and 1970s (see graph). According to population projections, world population will continue to grow until around 2050. The 2008 rate of growth has almost halved since its peak of 2.2% per year, which was reached in 1963. World births have levelled off at about 134-million-per-year, since their peak at 163-million in the late 1990s, and are expected to remain constant. However, deaths are only around 57 million per year, and are expected to increase to 90 million by the year 2050. Since births outnumber deaths, the world’s population is expected to reach about 9 billion by the year 2040.
A dramatic population bottleneck is theorized for the period around 70,000 BCE (see Toba catastrophe theory). After this time and until the development of agriculture, it is estimated that the world population stabilized at about one million people whose subsistence entailed hunting and foraging, a lifestyle that by its nature ensured a low population density. It is estimated that over 55 million people lived in the combined eastern and western Roman Empire (300–400 AD).The Plague of Justinian caused Europe’s population to drop by around 50% between 541 and the 700s.The Black Death pandemic in the 14th century may have reduced the world’s population from an estimated 450 million to between 350 and 375 million in 1400.
At the founding of the Ming dynasty in 1368, China‘s population was reported to be close to 60 million, and toward the end of the dynasty in 1644 it might have approached 150 million.New crops that had come to Asia from the Americas via the Spanish colonizers in the 16th century contributed to the population growth. Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of 90 to 95% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza.Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.
During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically.The percentage of the children born in London who died before the age of five decreased from 74.5% in 1730-1749 to 31.8% in 1810-1829.Europe’s population doubled during the 18th century, from roughly 100 million to almost 200 million, and doubled again during the 19th century. The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941.