Introduvtive Survey of world Population

In demographics, the world population is the total number of humans currently living. As of August 2016, it was estimated at 7.4 billion. The United Nations estimates it will further increase to 11.2 billion in the year 2100.

World population has experienced continuous growth since the end of the Great Famine of 1315–17 and the Black Death in 1350, when it was near 370 million. The highest population growth rates – global population increases above 1.8% per year – occurred between 1955-1975 peaking to 2.06% between 1965 -1970. The growth rate has declined to 1.18% between 2010-2015 and is projected to decline to 0.13% by the year 2100. Total annual births were highest in the late 1980s at about 139 million, and are now expected to remain essentially constant at their 2011 level of 135 million, while deaths number 56 million per year and are expected to increase to 80 million per year by 2040. World population reached 7 billion on October 31, 2011 according to the United Nations Population Fund, and on March 12, 2012 according to the United States Census Bureau.

The median age of the world's population was estimated to be 30.1 years in 2016, with the male median age estimated to be 29.4 years and female, 30.9 years.

The 2012 UN projections show a continued increase in population in the near future with a steady decline in population growth rate; the global population is expected to reach between 8.3 and 10.9 billion by 2050. 2003 UN Population Division population projections for the year 2150 range between 3.2 and 24.8 billion. One of many independent mathematical models supports the lower estimate, while a 2014 estimate forecasts between 9.3 and 12.6 billion in 2100, and continued growth thereafter. Some analysts have questioned the sustainability of further world population growth, highlighting the growing pressures on the environment, global food supplies, and energy resources.

Estimates on the total number of humans who have ever lived range in the order of 106 to 108 billion.

Population by region

Six of the Earth's seven continents are permanently inhabited on a large scale. Asia is the most populous continent, with its 4.3 billion inhabitants accounting for 60% of the world population. The world's two most populated countries alone, China and India, together constitute about 37% of the world's population. Africa is the second most populated continent, with around 1 billion people, or 15% of the world's population. Europe's 733 million people make up 12% of the world's population as of 2012, while the Latin American and Caribbean regions are home to around 600 million (9%). Northern America, primarily consisting of the United States, Mexico, and Canada, has a population of around 352 million (5%), and Oceania, the least-populated region, has about 35 million inhabitants (0.5%).Though it is not permanently inhabited by any fixed population, Antarctica has a small, fluctuating international population, based mainly in polar science stations. This population tends to rise in the summer months and decrease significantly in winter, as visiting researchers return to their home countries.

Projections

Main articles: World population estimates and Projections of population growth

Long-term global population growth is difficult to predict. The United Nations and the US Census Bureau both give different estimates – according to the UN, the world population reached seven billion in late 2011, while the USCB asserted that this occurred in March 2012. The UN has issued multiple projections of future world population, based on different assumptions. From 2000 to 2005, the UN consistently revised these projections downward, until the 2006 revision, issued on March 14, 2007, revised the 2050 mid-range estimate upwards by 273 million.

Average global birth rates are declining fast, but vary greatly between developed countries (where birth rates are often at or below replacement levels) and developing countries (where birth rates typically remain high). Different ethnicities also display varying birth rates. Death rates can change rapidly due to disease epidemics, wars and other mass catastrophes, or advances in medicine.