World population milestones

Estimated and projected populations of the world and its inhabited continents from 1950. The shaded regions correspond to range of projections by the United Nations Department of Economic and Social Affairs; for example, it estimates that the world population will reach 8 billion between 2022 and 2035.

World population milestones, such as reaching particular population counts, have been unnoticed until the 20th century, since there were no reliable data on global population dynamics.

It is estimated that the population of the world reached one billion for the first time in 1804. It would be another 123 years before it reached two billion in 1927, but it took only 33 years to rise by another billion people, reaching three billion in 1960. Thereafter, the global population reached four billion in 1974, five billion in 1987, six billion in 1999 and, by some estimates, seven billion in October 2011 with other estimates being in March 2012. It is projected to reach eight billion by 2024–2030. According to current projections, the world's population is likely to reach around nine billion by 2045–2050, with alternative scenarios ranging from a low of 7.4 billion to a high of more than 10.6 billion. Projected figures vary depending on underlying statistical assumptions and which variables are manipulated in projection calculations, especially the fertility variable. Long-range predictions to 2150 range from a population decline to 3.2 billion in the 'low scenario', to 'high scenarios' of 24.8 billion. One scenario predicts a massive increase to 256 billion by 2150, assuming fertility remains at 1995 levels.

World population milestones (USCB estimates)

Population (in billions)	1		2		3		4		5		6		7		8		9
Year	1804		1927		1960		1974		1987		1999		2011		2027		2046
Years elapsed	––		123		33		14		13		12		12		16		19

Billionth milestone days

There is no estimation for the exact day or month the world's population surpassed each of the one and two billion marks. The days of three and four billion were not officially noted, but the International Database of the United States Census Bureau places them in July 1959 and April 1974.

The Day of 5 billion

The Day of Five billion, 11 July 1987, was designated by the United Nations Population Fund as the approximate day on which world population reached five billion. Matej Gašpar from Zagreb, Croatia (then SR Croatia, SFR Yugoslavia), was chosen as the symbolic 5-billionth concurrently alive person on Earth. The honor went to Zagreb because the 1987 Summer Universiade was taking place in the city at the time.

The Day of 6 billion

The United Nations Population Fund designated 12 October 1999 as the approximate day on which world population reached six billion. It was officially designated The Day of Six billion. Demographers do not universally accept this date as being exact. In fact there has been subsequent research which places the day of six billion to be nearer to 18 June or 19 June 1999. The International Programs division of the United States Census Bureau estimated that the world population reached six billion on 21 April 1999.^{[citation needed]}

On the Day of Six billion, UN Secretary-General Kofi Annan was in Sarajevo, Bosnia and Herzegovina to monitor the Dayton Agreement. At midnight he went to Koševo Hospital, where Adnan Mević, born at 12.01 am, was named the symbolic 6 billionth concurrently alive person on Earth. He is the first son of Fatima Mević and Jasminko Helać and weighed 3.5 kg.

The Day of 7 billion

Main article: Day of Seven Billion

The "Day of Seven Billion" was targeted by the United States Census Bureau to be in March 2012, while the Population Division of the United Nations suggested 31 October 2011, and the latter date has been officially designated by the United Nations Population Fund (UNFPA) as the approximate day on which the world's population reached seven billion people. United Nations Secretary General Ban-Ki Moon is to speak at the United Nations building in New York City on this new milestone in the size of world population and the issues that it will raise, along with promoting the UNFPA's new program named 7 billion Actions, which will seek to: "[build] global awareness around the opportunities and challenges associated with a world of seven billion people" and inspire individuals and organizations to take action.

The Day of 8 billion

Estimated to be in 2027 (see table)

The Day of 9 billion

Estimated to be in 2046 (see table)

See also

• United States Population Clock