Projections of population growth
According to current projections of population growth, the world population of humans will continue to grow until at least 2050, with the estimated population, based on current growth trends, to reach 9 billion in 2040, and some predictions putting the population in 2050 as high as 11 billion. World population passed the 7 billion mark on October 31, 2011.
According to the United Nations' World Population Prospects report, the world population is currently growing by approximately 74 million people per year. Current United Nations predictions estimate that the world population will reach 9.0 billion around 2050, assuming a decrease in average fertility rate from 2.5 down to 2.0.
Almost all growth will take place in the less developed regions, where today's 98.3 million population of underdeveloped countries is expected to increase to 7.8 billion in 2050. By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion. An exception is the United States population, which is expected to increase 31% from 305 million in 2008 to 400 million in 2050 due to projected net international migration. In 2000–2005, the average world fertility was 2.65 children per woman, about half the level in 1950–1955 (5 children per woman). In the medium variant, global fertility is projected to decline further to 2.05 children per woman.
During 2005–2050, twelve countries are expected to account for half of the world's projected population increase: India, China, United States, Indonesia, Nigeria, Pakistan, Brazil, Democratic Republic of the Congo, Ethiopia, Philippines, Mexico and Egypt, listed according to the size of their contribution to population growth.
Global life expectancy at birth, which is estimated to have risen from 46 years in 1950–1955 to 65 years in 2000–2005, is expected to keep rising to reach 75 years in 2045–2050. In the more developed regions, the projected increase is from 75 years today to 82 years by mid-century. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to be 66 years in 2045–2050. The population of 31 countries or areas, including Ukraine, Romania, Japan and most of the successor States of the former Soviet Union, is expected to be lower in 2050 than in 2005.
Projected migration to Western countries
According to the United Nations, during 2005–2050 the net number of international migrants to more developed regions is projected to be 98 million. Because deaths are projected to exceed births in the more developed regions by 73 million during 2005–2050, population growth in those regions will largely be due to international migration. In 2000–2005, net migration in 28 countries either prevented population decline or doubled at least the contribution of natural increase (births minus deaths) to population growth. These countries include Austria, Canada, Croatia, Denmark, Germany, Italy, Portugal, Qatar, Singapore, Spain, Sweden, the United Arab Emirates and the United Kingdom. Birth rates are low in a small percentage of developing countries.
By 2050 (Medium variant), India will have 1.66 billion people, China 1.42 billion, United States 440 million, Indonesia 327 million, Nigeria 306 million, Pakistan 282 million, Brazil 261 million, Democratic Republic of the Congo 196 million, Ethiopia 189 million, Philippines 171 million, Mexico 166 million, Egypt 151 million, Bangladesh 145 million, Russia 129 million, Tanzania 120 million, Vietnam 113 million, Japan 107 million, Iran 101 million, Turkey 97 million, Kenya 90 million, Uganda 84 million, Germany 81 million, United Kingdom 76 million and Colombia 70 million, .
World population in 2050
- Asia – 5.2 billion
- Africa – 2.4 billion
- North America, South America, & the Caribbean – 1.2 billion
- Europe – 709 million
- Oceania – 56.9 million
Walter Greiling projected in the 1950s that world population would reach a peak of about nine billion, in the 21st century, and then stop growing after a readjustment of the Third World and a sanitation of the tropics. Recent extrapolations from available figures for population growth show that the population of Earth will stop increasing around 2070.
The United Nations Department of Economic and Social Affairs report (2004) projects the world population to peak at 9.22 billion in 2075. After reaching this maximum the world population is projected to decline slightly and then resume increasing slowly, to reach a level of 8.97 billion by 2300, about the same as the projected 2050 figure. A 2014 paper by demographers from several universities and the United Nations Population Division forecast that the world's population will reach about 10.9 billion in 2100 and continue growing thereafter. An alternative scenario is given by Jorgen Randers, who argues that traditional projections insufficiently take into account the downward impact of global urbanization on fertility. Randers' "most likely scenario" reveals a peak in the world population in the early 2040s at about 8.1 billion people, followed by decline.
These projected growth patterns depend on assumptions about vital rates. Total fertility is assumed to continue to decline, at varying paces depending on circumstances in individual countries, to a below-replacement level of 1.85 children per woman by mid century. Countries already at this level or below, and other countries when they reach it, will eventually return to replacement over a period of a century and stay at replacement going forward. All countries are projected to have reached replacement fertility by 2175.
Some of the authors of the report say that life expectancy is assumed to rise slowly and continuously. The projections in the report assume this with no upper limit, though at a slowing pace depending on circumstances in individual countries. By 2100, the report assumes life expectancy to be from 66 to 97 years, and by 2300 from 87 to 106 years, depending on the country. Based on that assumption, they said that rising life expectancy will produce small but continuing population growth by the end of the projections, ranging from 0.03 to 0.07 percent annually.
However, based on recent research, many expect that life expectancy will leap ahead and indefinite human lifespans are not necessarily unfeasible. This could significantly raise the estimates. In an essay within the U.N. report, Tim Dyson said,
- "A rapid increase in life expectancy, which would raise the population pyramids, seems within reach, since it responds to an old and powerful demand for longevity."
Most populous nations by 2030
The United Nations Population Fund has calculated, based on current trends, the future population of the world's countries. These figures can easily change as events such as wars, diseases, breakthroughs in life extension technologies, or dramatic demographic changes would all greatly affect the results. The study projected the world population in 2030 to be 8.321 billion.
|03||03||=||United States (demographics)||361,680,000||310,384,000||+16.5%|
Projections for after 2050 have usually assumed that fertility rates will have declined by then and the population will be stable or will decrease. However, a study in 2014 found that fertility rates in Africa have leveled off at around 4.6 instead of continuing to decline, and that consequently world population may be as high as 12 billion by 2100. Reasons for the continuing high fertility rate include better survival rates with respect to HIV, and lack of availability of contraception. Another study on the other hand concludes that education of women will lead to low fertility rates even in Africa. Evolutionary biology also suggests the demographic transition may reverse itself; in addition, recent evidence suggests birth rates may be rising in the 21st century in the developed world.
Population projections of the 101 largest cities in the 21st century
Large urban areas are hubs of economic development and innovation, with larger cities underpinning regional economies and local and global sustainability initiatives. Currently, 757 million people reside in the 101 largest cities; these cities are home to 11% of the world’s population. By the end of the century, the world population is projected to grow, with estimates ranging from 6.9 billion to 13.1 billion; the percentage of people residing in the 101 larger cities is estimated to be 15% to 23%.
The 101 cities with the largest population projections for the years 2025, 2050, 2075, and 2100 are listed below.
|Rank||City||Projected Population (millions) 2025||City||Projected Population (millions) 2050||City||Projected Population (millions) 2075||City||Projected Population (millions) 2100|
|2||Mumbai||26.39||Delhi||36.16||Lagos||55.26||Dar es Salaam||73.68|
|7||New York||20.63||Tokyo||32.62||Dhaka||42.45||Blantyre City||56.78|
|8||Kolkata||20.56||Karachi||31.70||Dar es Salaam||37.49||Khartoum||56.59|
|17||Los Angeles||13.67||Los Angeles||16.42||Lahore||23.88||Dhaka||38.54|
|18||Rio de Janeiro||13.41||Chennai||16.28||Addis Ababa||23.71||Mogadishu||36.37|
|19||Jakarta||12.36||Khartoum||16.00||Mexico City||22.80||Addis Ababa||35.82|
|20||Istanbul||12.10||Dar es Salaam||15.97||Chennai||22.21||Lusaka||35.76|
|28||Chicago||9.93||Rio de Janeiro||14.29||Luanda||17.15||Hyderabad||23.17|
|36||Hyderabad||9.09||Ho Chi Minh City||11.86||Pune||14.91||Bamako||17.85|
|42||Ho Chi Minh City||8.15||Tehran||11.00||Abidjan||14.27||Conakry||14.79|
|49||Pune||6.80||Tianjin||10.15||Rio de Janeiro||12.35||Sao Paulo||13.77|
|50||Hano||6.75||Sana'a||10.05||Ho Chi Minh City||12.32||Buenos Aires||13.75|
|65||Dar es Salaam||5.69||Santiago (BR)||7.49||Kigali||9.79||Benin City||9.66|
|69||Tonala||5.37||Belo Horizonte||7.19||Hong Kong||9.46||Ho Chi Minh City||9.05|
|73||Barcelona||5.18||Jaipur||6.91||Giza||8.96||Rio de Janeiro||8.62|
|82||Washington DC||4.89||Dallas-Fort Worth||6.51||Nagpur||7.86||Port Harcourt||8.15|
|86||Porto Alegre||4.63||Zapopan||6.22||Seoul||7.52||Bat Dambang||7.98|
|95||Recife||4.35||Washington DC||5.87||Benin City||6.97||Brazzaville||7.45|
- Human overpopulation
- Pledge two or fewer (campaign for smaller families)
- Population growth
- World population estimates
- "World Population Clock". Worldometers. Retrieved 24 October 2011.
- International Data Base (IDB) — World Population
- World Population Prospects
- United Nations Population Division Home Page, United Nations Department of Economic and Social Affairs
- Microsoft Word – WorldPOP2300.doc
- http://www.un.org/News/Press/docs/2005/pop918.doc.html[dead link]
- Walter Greiling: Wie werden wir leben? ("How are we going to live?") Econ publishers, Munich 1954
- Ciro Pabón y Ciro Pabón, Manual de Urbanismo, Editorial Leyer, Bogotá, 2007, ISBN 978-958-711-296-2
- United Nations Department of Economic and Social Affairs. World Population to 2300. 2004. Executive Summary, Page 2.
- Gerland, P.; Raftery, A. E.; Ev Ikova, H.; Li, N.; Gu, D.; Spoorenberg, T.; Alkema, L.; Fosdick, B. K.; Chunn, J.; Lalic, N.; Bay, G.; Buettner, T.; Heilig, G. K.; Wilmoth, J. (September 14, 2014). "World population stabilization unlikely this century". Science (AAAS) 346 (6206): 234. doi:10.1126/science.1257469. ISSN 1095-9203. PMID 25301627. Retrieved September 21, 2014.
- Randers, Jorgen (2012). 2052: A Global Forecast for the Next Forty Years. Vermont: Chelsea Green Publishing. p. 62.
- Newmark PA, Sánchez Alvarado A (2002). Not your father's planarian: a classic model enters the era of functional genomics. Nat Rev Genet 3:210-219. PMID 11972158
- Bavestrello, Giorgio; Christian Sommer and Michele Sarà (1992). Bi-directional conversion in Turritopsis nutricula (Hydrozoa). Scientia Marina 56 (2–3): 137–140
- Martínez DE (1998). Mortality patterns suggest lack of senescence in hydra. Exp Gerontol 33(3):217-225. PMID 9615920
- World Population Prospects, the 2010 Revision[dead link]
- Andy Coghlan (27 Sep 2014). "Global population may boom well beyond the year 2050". New Scientist: 11.
- Patrick Gerland, Adrian Raftery; et al. (18 Sep 2014). "World population stabilization unlikely this century". Science. doi:10.1126/science.1257469.
- Can we be sure the world's population will stop rising?, BBC News, 13 October 2012
- Hoornweg, Daniel; Pope, Kevin (January 2014). "Population predictions of the 101 largest cities in the 21st century" (PDF). Global Cities Institute (Working Paper No. 4).