Events on October 31 in history

The global population of humans reaches seven billion. This day is now recognized by the United Nations as the Day of Seven Billion.

The Day of Seven Billion, October 31, 2011, is the day that 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 spoke 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.

In demographics, the term world population is often used to refer to the total number of humans currently living, and was estimated to have exceeded 7.9 billion as of November 2021. It took over two million years of human prehistory and history for the human population to reach one billion and only 200 years more to grow to 7 billion.The human population has experienced continuous growth following the Great Famine of 1315–1317 and the end of the Black Death in 1350, when it was near 370,000,000.

The highest global population growth rates, with increases of over 1.8% per year, occurred between 1955 and 1975 – peaking at 2.1% between 1965 and 1970. The growth rate declined to 1.2% between 2010 and 2015 and is projected to decline further in the course of the 21st century. The global population is still increasing, but there is significant uncertainty about its long-term trajectory due to changing rates of fertility and mortality. The UN Department of Economics and Social Affairs projects between 9–10 billion people by 2050, and gives an 80% confidence interval of 10–12 billion by the end of the 21st century. Other demographers predict that the human population will begin to decline in the second half of the 21st century.

Birth rates were highest in the late 1980s at about 139 million, and as of 2011 were expected to remain essentially constant at a level of 135 million, while the mortality rate numbered 56 million per year and were expected to increase to 80 million per year by 2040.

The median age of human beings as of 2020 is 31 years.