In biology, a population is all the organisms of the same group or species, which live in a particular geographical area, and have the capability of interbreeding. The area of a sexual population is the area where inter-breeding is potentially possible between any pair within the area, and where the probability of interbreeding is greater than the probability of cross-breeding with individuals from other areas.
In sociology, population refers to a collection of humans. Demography is a social science which entails the statistical study of human populations. Population in simpler terms is the number of people in a city or town, region, country or world; population is usually determined by a process called census (a process of collecting, analyzing, compiling and publishing data)
This article refers mainly to human population.
In population genetics a sex population is a set of organisms in which any pair of members can breed together. This means that they can regularly exchange gametes to produce normally-fertile offspring, and such a breeding group is also known therefore as a Gamo deme. This also implies that all members belong to the same species. If the Gamo deme is very large (theoretically, approaching infinity), and all gene alleles are uniformly distributed by the gametes within it, the Gamo deme is said to be panmictic. Under this state, allele (gamete) frequencies can be converted to genotype (zygote) frequencies by expanding an appropriate quadratic equation, as shown by Sir Ronald Fisher in his establishment of quantitative genetics.
This seldom occurs in Nature: localization of gamete exchange – through dispersal limitations, preferential mating, cataclysm, or other cause – may lead to small actual Gamo demes which exchange gametes reasonably uniformly within themselves but are virtually separated from their neighboring Gamo demes. However, there may be low frequencies of exchange with these neighbors. This may be viewed as the breaking up of a large sexual population (panmictic) into smaller overlapping sexual populations. This failure of panmixia leads to two important changes in overall population structure: (1) the component Gamo demos vary (through gamete sampling) in their allele frequencies when compared with each other and with the theoretical panmictic original (this is known as dispersion, and its details can be estimated using expansion of an appropriate binomial equation); and (2) the level of homozygosity rises in the entire collection of Gamo demes. The overall rise in homozygosity is quantified by the inbreeding coefficient (f or φ). Note that all homozygotes are increased in frequency – both the deleterious and the desirable. The mean phenotype of the Gamo demes collection is lower than that of the panmictic original – which is known as inbreeding depression. It is most important to note, however, that some dispersion lines will be superior to the panmictic original, while some will be about the same, and some will be inferior. The probabilities of each can be estimated from those binomial equations. In plant and animal breeding, procedures have been developed which deliberately utilize the effects of dispersion (such as line breeding, pure-line breeding, backcrossing). It can be shown that dispersion-assisted selection leads to the greatest genetic advance (ΔG=change in the phenotypic mean), and is much more powerful than selection acting without attendant dispersion. This is so for both allogamous (random fertilization) and autogamous (self-fertilization) Gamo demes.
In ecology, the population of a certain species in a certain area can be estimated using the Lincoln Index.
According to the United States Census Bureau the world's population was about 7.55 billion in 2019  and that the 7 billion number was surpassed on 12 March 2012. According to a separate estimate by the United Nations, Earth’s population exceeded seven billion in October 2011, a milestone that offers unprecedented challenges and opportunities to all of humanity, according to UNFPA, the United Nations Population Fund.
According to papers published by the United States Census Bureau, the world population hit 6.5 billion on 24 February 2006. The United Nations Population Fund designated 12 October 1999 as the approximate day on which world population reached 6 billion. This was about 12 years after world population reached 5 billion in 1987, and 6 years after world population reached 5.5 billion in 1993. The population of countries such as Nigeria, is not even known to the nearest million, so there is a considerable margin of error in such estimates.
Researcher Carl Haub calculated that a total of over 100 billion people have probably been born in the last 2000 years.
Population growth increased significantly as the Industrial Revolution gathered pace from 1700 onwards. The last 50 years have seen a yet more rapid increase in the rate of population growth due to medical advances and substantial increases in agricultural productivity, particularly beginning in the 1960s, made by the Green Revolution. In 2017 the United Nations Population Division projected that the world's population will reach about 9.8 billion in 2050 and 11.2 billion in 2100.
In the future, the world's population is expected to peak, after which it will decline due to economic reasons, health concerns, land exhaustion and environmental hazards. According to one report, it is very likely that the world's population will stop growing before the end of the 21st century. Further, there is some likelihood that population will actually decline before 2100. Population has already declined in the last decade or two in Eastern Europe, the Baltics and in the Commonwealth of Independent States.
The population pattern of less-developed regions of the world in recent years has been marked by gradually increasing birth rates. These followed an earlier sharp reduction in death rates. This transition from high birth and death rates to low birth and death rates is often referred to as the demographic transition.
Human population control is the practice of altering the rate of growth of a human population. Historically, human population control has been implemented with the goal of increasing the rate of population growth. In the period from the 1950s to the 1980s, concerns about global population growth and its increasing effects on poverty, environmental degradation, and political stability led to efforts to reduce population growth rates. While population control can involve measures that improve people's lives by giving them greater control of their reproduction, a few programs, most notably the Chinese government's one-child per family policy, have resorted to coercive measures. To control of population structure,it measures through efficient mixed-model association (EMMA) method, which corrects for population structure and genetic relatedness in model organism association mapping. 
In the 1978s, stress increased between population control advocates and women's health activists who advanced women's reproductive rights as part of a human rights-based approach. Growing opposition to the narrow population control focus led to a significant change in population control policies in the early 1980s.
a community of animals, plants, or humans among whose members interbreeding occurs
The 15th Indian Census was conducted in two phases, house listing and population enumeration. House listing phase began on 1 April 2010 and involved collection of information about all buildings. Information for National Population Register was also collected in the first phase, which will be used to issue a 12-digit unique identification number to all registered Indian residents by Unique Identification Authority of India (UIDAI). The second population enumeration phase was conducted between 9 and 28 February 2011. Census has been conducted in India since 1872 and 2011 marks the first time biometric information was collected. According to the provisional reports released on 31 March 2011, the Indian population increased to 1.21 billion with a decadal growth of 17.70%. Adult literacy rate increased to 74.04% with a decadal growth of 9.21%. The motto of the census was 'Our Census, Our future'.
Spread across 29 states and 7 union territories, the census covered 640 districts, 5,924 sub-districts, 7,935 towns and more than 600,000 villages. A total of 2.7 million officials visited households in 7,935 towns and 600,000 villages, classifying the population according to gender, religion, education and occupation. The cost of the exercise was approximately ₹2,200 crore (US$310 million) – this comes to less than $0.50 per person, well below the estimated world average of $4.60 per person. Conducted every 10 years, this census faced big challenges considering India's vast area and diversity of cultures and opposition from the manpower involved.
Information on castes was included in the census following demands from several ruling coalition leaders including Lalu Prasad Yadav, Sharad Yadav and Mulayam Singh Yadav supported by opposition parties Bharatiya Janata Party, Akali Dal, Shiv Sena and Anna Dravida Munnetra Kazhagam. Information on caste was last collected during the British Raj in 1931. During the early census, people often exaggerated their caste status to garner social status and it is expected that people downgrade it now in the expectation of gaining government benefits. There was speculation that there would be a caste-based census conducted in 2011, the first time for 80 years (last was in 1931), to find the exact population of the "Other Backward Classes" (OBCs) in India. This was later accepted and the Socio Economic and Caste Census 2011 was conducted whose first findings were revealed on 3 July 2015 by Union Finance Minister Arun Jaitley. Mandal Commission report of 1980 quoted OBC population at 52%, though National Sample Survey Organisation (NSSO) survey of 2006 quoted OBC population at 41%There is only one instance of a caste-count in post-independence India. It was conducted in Kerala in 1968 by the Communist government under E M S Namboodiripad to assess the social and economic backwardness of various lower castes. The census was termed Socio-Economic Survey of 1968 and the results were published in the Gazetteer of Kerala, 1971.Americans
Americans are nationals and citizens of the United States of America. Although nationals and citizens make up the majority of Americans, some dual citizens, expatriates, and permanent residents may also claim American nationality. The United States is home to people of many different ethnic origins. As a result, American culture and law does not equate nationality with race or ethnicity, but with citizenship and permanent allegiance.English-speakers, and even speakers of many other languages, typically use the term "American" to exclusively mean people of the United States; this developed from its original use to differentiate English people of the American colonies from English people of England. The word "American" can also refer to people from the Americas in general (see names for United States citizens).Census
A census is the procedure of systematically acquiring and recording information about the members of a given population. The term is used mostly in connection with national population and housing censuses; other common censuses include agriculture, business, and traffic censuses. The United Nations defines the essential features of population and housing censuses as "individual enumeration, universality within a defined territory, simultaneity and defined periodicity", and recommends that population censuses be taken at least every 10 years. United Nations recommendations also cover census topics to be collected, official definitions, classifications and other useful information to co-ordinate international practice.The word is of Latin origin: during the Roman Republic, the census was a list that kept track of all adult males fit for military service. The modern census is essential to international comparisons of any kind of statistics, and censuses collect data on many attributes of a population, not just how many people there are. Censuses typically began as the only method of collecting national demographic data, and are now part of a larger system of different surveys. Although population estimates remain an important function of a census, including exactly the geographic distribution of the population, statistics can be produced about combinations of attributes e.g. education by age and sex in different regions. Current administrative data systems allow for other approaches to enumeration with the same level of detail but raise concerns about privacy and the possibility of biasing estimates.A census can be contrasted with sampling in which information is obtained only from a subset of a population; typically main population estimates are updated by such intercensal estimates. Modern census data are commonly used for research, business marketing, and planning, and as a baseline for designing sample surveys by providing a sampling frame such as an address register. Census counts are necessary to adjust samples to be representative of a population by weighting them as is common in opinion polling. Similarly, stratification requires knowledge of the relative sizes of different population strata which can be derived from census enumerations. In some countries, the census provides the official counts used to apportion the number of elected representatives to regions (sometimes controversially – e.g., Utah v. Evans). In many cases, a carefully chosen random sample can provide more accurate information than attempts to get a population census.Demographics of India
India is the second most populated country in the world with nearly a fifth of the world's population. According to the 2017 revision of the World Population Prospects, the population stood at 1,324,171,354.
During 1975–2010 the population doubled to 1.2 billion. The Indian population reached the billion mark in 1998. India is projected to be the world's most populous country by 2024, surpassing the population of China. It is expected to become the first political entity in history to be home to more than 1.5 billion people by 2030, and its population is set to reach 1.7 billion by 2050. Its population growth rate is 1.13%, ranking 112th in the world in 2017.India has more than 50% of its population below the age of 25 and more than 65% below the age of 35. It is expected that, in 2020, the average age of an Indian will be 29 years, compared to 37 for China and 48 for Japan; and, by 2030, India's dependency ratio should be just over 0.4.India has more than two thousand ethnic groups, and every major religion is represented, as are four major families of languages (Indo-European, Dravidian, Austroasiatic and Sino-Tibetan languages) as well as two language isolates (the Nihali language spoken in parts of Maharashtra and the Burushaski language spoken in parts of Jammu and Kashmir (Kashmir).
Further complexity is lent by the great variation that occurs across this population on social parameters such as income and education. Only the continent of Africa exceeds the linguistic, genetic and cultural diversity of the nation of India.The sex ratio is 944 females for 1000 males (2016) (940 per 1000 in 2011) This ratio has been showing an upwards trend for the last two decades after a continuous decline in the last century.Demography
Demography (from prefix demo- from Ancient Greek δῆμος dēmos meaning "the people", and -graphy from γράφω graphō, implies "writing, description or measurement") is the statistical study of populations, especially human beings. As a very general science, it can analyze any kind of dynamic living population, i.e., one that changes over time or space (see population dynamics). Demography encompasses the study of the size, structure, and distribution of these populations, and spatial or temporal changes in them in response to birth, migration, aging, and death. Based on the demographic research of the earth, earth's population up to the year 2050 and 2100 can be estimated by demographers. Demographics are quantifiable characteristics of a given population.
Demographic analysis can cover whole societies or groups defined by criteria such as education, nationality, religion, and ethnicity. Educational institutions usually treat demography as a field of sociology, though there are a number of independent demography departments.Formal demography limits its object of study to the measurement of population processes, while the broader field of social demography or population studies also analyses the relationships between economic, social, cultural, and biological processes influencing a population.Demography of the United States
The United States is the third most populous country in the world with an estimated population of 328,285,992 as of January 12, 2019.The United States Census Bureau shows a population increase of 0.75% for the twelve-month period ending in July 2012. Though high by industrialized country standards, this is below the world average annual rate of 1.1%. The total fertility rate in the United States estimated for 2017 is 1.77 children per woman, which is below the replacement fertility rate of approximately 2.1.
The American population almost quadrupled during the 20th century—at a growth rate of about 1.3% a year—from about 76 million in 1900 to 281 million in 2000. It is estimated to have reached the 200 million mark in 1967, and the 300 million mark on October 17, 2006. Population growth is fastest among minorities as a whole, and according to the Census Bureau's estimation for 2012, 50.4% of American children under the age of 1 belonged to racial and ethnic minority groups.White people constitute the majority of the U.S. population, with a total of about 245,532,000 or 77.7% of the population as of 2013. Non-Hispanic whites make up 62.6% of the country's population. The non-Hispanic white population of the US is expected to fall below 50% by 2045.Hispanic and Latino Americans accounted for 48% of the national population growth of 2.9 million between July 1, 2005, and July 1, 2006. Immigrants and their U.S.-born descendants are expected to provide most of the U.S. population gains in the decades ahead.The Census Bureau projects a U.S. population of 417 million in 2060, a 38% increase from 2007 (301.3 million), and the United Nations estimates the U.S. population will be 402 million in 2050, an increase of 32% from 2007. In an official census report, it was reported that 54.4% (2,150,926 out of 3,953,593) of births in 2010 were non-Hispanic white. This represents an increase of 0.3% compared to the previous year, which was 54.1%.Islam by country
Adherents of Islam constitute the world's second largest religious group. According to a study in 2015, Islam has 1.8 billion adherents, making up about 24.1% of the world population. Most Muslims are either of two denominations: Sunni (80–90%, roughly 1.5 billion people) or Shia (10–20%, roughly 170–340 million people). Islam is the dominant religion in Central Asia, Indonesia, Middle East, North Africa, the Sahel and some other parts of Asia. The diverse Asia-Pacific region contains the highest number of Muslims in the world, easily surpassing the Middle East and North Africa.South Asia contains the largest population of Muslims in the world. One-third of the Muslims are of South Asian origin. Islam is the largest religion in the Maldives, Afghanistan, Pakistan, and Bangladesh, and second-largest in India.
The various Hamito-Semitic (including Arab, Berber), Turkic, and Iranic countries of the greater Middle East-North Africa (MENA) region, where Islam is the dominant religion in every country other than Israel, hosts 23% of world Muslims.
The country with the single largest population of Muslims is Indonesia in Southeast Asia, which on its own hosts 13% of the world's Muslims. Together, the Muslims in the countries of Southeast Asia constitute the world's third-largest population of Muslims. In the countries of the Malay Archipelago Muslims are majorities in each country other than the Philippines, Singapore, and East Timor.
About 15% of Muslims reside in Sub-Saharan Africa, and sizeable Muslim communities are also found in the Americas, China, Russia, and Europe.Western Europe hosts many Muslim immigrant communities where Islam is the second-largest religion after Christianity, where it represents 6% of the total population or 24 million people. Converts and immigrant communities are found in almost every part of the world.List of United States cities by population
The following is a list of the most populous incorporated places of the United States. As defined by the United States Census Bureau, an "incorporated place" includes a variety of designations, including city, town, village, borough, and municipality. A few exceptional census-designated places (CDPs) are also included in the Census Bureau's listing of incorporated places. Consolidated city-counties represent a distinct type of government that includes the entire population of a county, or county equivalent. Some consolidated city-counties, however, include multiple incorporated places. This list presents only that portion (or "balance") of such consolidated city-counties that are not a part of another incorporated place.
This list refers only to the population of individual municipalities within their defined limits; the populations of other municipalities considered suburbs of a central city are listed separately, and unincorporated areas within urban agglomerations are not included. Therefore, a different ranking is evident when considering U.S. metropolitan area populations.List of cities in India by population
The following tables are the list of cities in India by population. Often cities are bifurcated into multiple regions (municipalities) which results in creation of cities within cities which may figure in the list. The entire work of this article is based on Census of India, 2011, conducted by the Office of the Registrar General and Census Commissioner, under Ministry of Home Affairs (India), Government of India.List of countries and dependencies by population
This is a list of countries and dependent territories by population. It includes sovereign states, inhabited dependent territories and, in some cases, constituent countries of sovereign states, with inclusion within the list being primarily based on the ISO standard ISO 3166-1. For instance, the United Kingdom is considered as a single entity, while the constituent countries of the Kingdom of the Netherlands are considered separately. In addition, this list includes certain states with limited recognition not found in ISO 3166-1.
Also given in percent is each country's population compared with the population of the world, which the United Nations estimates at 7.7 billion as of today.List of countries and dependencies by population density
This is a list of countries and dependent territories ranked by population density, measured by the number of human inhabitants per square kilometer.
The list includes sovereign states and self-governing dependent territories based upon the ISO standard ISO 3166-1. The list also includes but does not rank unrecognized but de facto independent countries. The figures in the following table are based on areas including inland water bodies (lakes, reservoirs, rivers).
Figures used in this article are mainly based on the latest censuses and official estimates (or projections). Where there is not such updated national data available, figures are based on the online projections provided by the Population Division of the United Nations Department of Economic and Social Affairs.List of districts in India
A district (zilā) is an administrative division of an Indian state or territory. In some cases districts are further subdivided into sub-divisions, and in others directly into tehsils or talukas. As of 2019 there are a total of 725 districts, up from the 640 in the 2011 Census of India and the 593 recorded in the 2001 Census of India.District officials include:
District Magistrate or Deputy Commissioner or District Collector, an officer of the Indian Administrative Service, in charge of administration and revenue collection
Superintendent of Police or Senior Superintendent of Police or Deputy Commissioner of Police, an officer belonging to the Indian Police Service, responsible for maintaining law and order
Deputy Conservator of Forests, an officer belonging to the Indian Forest Service, entrusted with the management of the forests, environment and wildlife of the districtEach of these officials is aided by officers from the appropriate branch of the state government.
Most districts have a distinct headquarters; but the districts of Mumbai City, in Maharashtra, and Chennai, in Tamil Nadu, are examples where there is no distinct district headquarters, although there are district collectors.
Mahe of Puducherry is the smallest (9 km2) district of India by area while Kutch of Gujarat is the largest (45,652 km2) district of India by area.List of largest cities
Determining the world's largest cities depends on which definitions of city are used, as well as the criteria used for size: this article focusses on population. The United Nations uses three definitions for what constitutes a city, as not all cities may be classified using the same criteria. Cities may be defined as the cities proper, the extent of their urban area, or their metropolitan regions.For a view of the largest cities by economic stature and integration within the global economy, see Globalization and World Cities Research Network.List of states and territories of the United States by population
The states and territories included in the United States Census Bureau's statistics include the 50 states, the District of Columbia and five permanently inhabited unincorporated island territories, including Puerto Rico.As of April 1, 2010, the date of the 2010 United States Census, the 9 most populous U.S. states contain slightly more than half of the total population. The 25 least populous states contain less than one-sixth of the total population. California, the most populous state, contains more people than the 21 least populous states combined, and Wyoming, the least populous state, has a population less than that of the 31 most populous U.S. cities.Population density
Population density (in agriculture: standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and most of the time to humans. It is a key geographical term. In simple terms population density refers to the number of people living in an area per kilometer square.Race and ethnicity in the United States
Race and ethnicity in the United States is a complex topic both because the United States of America has a racially and ethnically diverse population and because the country has a heavily racist history involving slavery and anti-miscegenation laws. At the federal level, race and ethnicity have been categorized separately.
The most recent United States Census officially recognized five racial categories (White American, Black or African American, Native American and Alaska Native, Asian American, and Native Hawaiian and Other Pacific Islander) as well as people of two or more races. The Census Bureau also classified respondents as "Hispanic or Latino" or "Not Hispanic or Latino", identifying Hispanic and Latino as an ethnicity (not a race), which comprises the largest minority group in the nation. The United States Supreme Court unanimously held that "race" is not limited to Census designations on the "race question" but extends to all ethnicities, and thus can include Jewish (which has the unique status as both an ethnicity and a religion), Arab, Hungarian, Laotian, Zulu, etc. The Census also asked an "Ancestry Question," which covers the broader notion of ethnicity, in the 2000 Census long form and the American Community Survey; the question will return in the 2020 Census.As of July 2016, White Americans are the racial majority. African Americans are the largest racial minority, comprising an estimated 12.7% of the population. Hispanic and Latino Americans are the largest ethnic minority, comprising an estimated 17.8% of the population. The White, non-Hispanic or Latino population make up 61.3% of the nation's total, with the total White population (including White Hispanics and Latinos) being 76.9%.White Americans are the majority in every census-defined region (Northeast, Midwest, South, West) and in every state except Hawaii, but contribute the highest proportion of the population in the Midwestern United States, at 85% per the Population Estimates Program (PEP) or 83% per the American Community Survey (ACS). Non-Hispanic Whites make up 79% of the Midwest's population, the highest ratio of any region. However, 35% of White Americans (whether all White Americans or non-Hispanic/Latino only) live in the South, the most of any region.Currently, 55% of the African American population lives in the South. A plurality or majority of the other official groups reside in the West. The latter region is home to 42% of Hispanic and Latino Americans, 46% of Asian Americans, 48% of American Indians and Alaska Natives, 68% of Native Hawaiians and Other Pacific Islanders, 37% of the "two or more races" population (Multiracial Americans), and 46% of those self-designated as "some other race".Standard deviation
In statistics, the standard deviation (SD, also represented by the lower case Greek letter sigma σ or the Latin letter s) is a measure that is used to quantify the amount of variation or dispersion of a set of data values. A low standard deviation indicates that the data points tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the data points are spread out over a wider range of values.
The standard deviation of a random variable, statistical population, data set, or probability distribution is the square root of its variance. It is algebraically simpler, though in practice less robust, than the average absolute deviation.
A useful property of the standard deviation is that, unlike the variance, it is expressed in the same units as the data.
In addition to expressing the variability of a population, the standard deviation is commonly used to measure confidence in statistical conclusions. For example, the margin of error in polling data is determined by calculating the expected standard deviation in the results if the same poll were to be conducted multiple times. This derivation of a standard deviation is often called the "standard error" of the estimate or "standard error of the mean" when referring to a mean. It is computed as the standard deviation of all the means that would be computed from that population if an infinite number of samples were drawn and a mean for each sample were computed.
It is very important to note that the standard deviation of a population and the standard error of a statistic derived from that population (such as the mean) are quite different but related (related by the inverse of the square root of the number of observations). The reported margin of error of a poll is computed from the standard error of the mean (or alternatively from the product of the standard deviation of the population and the inverse of the square root of the sample size, which is the same thing) and is typically about twice the standard deviation—the half-width of a 95 percent confidence interval.
In science, many researchers report the standard deviation of experimental data, and only effects that fall much farther than two standard deviations away from what would have been expected are considered statistically significant—normal random error or variation in the measurements is in this way distinguished from likely genuine effects or associations. The standard deviation is also important in finance, where the standard deviation on the rate of return on an investment is a measure of the volatility of the investment.
When only a sample of data from a population is available, the term standard deviation of the sample or sample standard deviation can refer to either the above-mentioned quantity as applied to those data or to a modified quantity that is an unbiased estimate of the population standard deviation (the standard deviation of the entire population).Urban area
An urban area or urban agglomeration is a human settlement with high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, towns, conurbations or suburbs. In urbanism, the term contrasts to rural areas such as villages and hamlets and in urban sociology or urban anthropology it contrasts with natural environment. The creation of early predecessors of urban areas during the urban revolution led to the creation of human civilization with modern urban planning, which along with other human activities such as exploitation of natural resources leads to human impact on the environment.
The world's urban population in 1950 of just 746 million has increased to 3.9 billion in the decades since. In 2009, the number of people living in urban areas (3.42 billion) surpassed the number living in rural areas (3.41 billion) and since then the world has become more urban than rural. This was the first time that the majority of the world's population lived in a city. In 2014 there were 7.2 billion people living on the planet, of which the global urban population comprised 3.9 billion. The Population Division of the United Nations Department of Economic and Social Affairs at that time predicted the urban population would grow to 6.4 billion by 2050, with 37% of that growth to come from three countries: China, India and Nigeria.Urban areas are created and further developed by the process of urbanization. Urban areas are measured for various purposes, including analyzing population density and urban sprawl.
Unlike an urban area, a metropolitan area includes not only the urban area, but also satellite cities plus intervening rural land that is socio-economically connected to the urban core city, typically by employment ties through commuting, with the urban core city being the primary labor market.World population
In demographics, the world population is the total number of humans currently living, and was estimated to have reached 7.6 billion people as of May 2018. It took over 200,000 years of human history for the world's population to reach 1 billion; and only 200 years more to reach 7 billion.World population has experienced continuous growth since the end of the Great Famine of 1315–1317 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 and 1975, peaking to 2.06% between 1965 and 1970. The growth rate has declined to 1.18% between 2010 and 2015 and is projected to decline further in the course of the 21st century. However, the global population is still growing and is projected to reach about 10 billion in 2050 and more than 11 billion in 2100.
Total annual births 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 deaths numbered 56 million per year and were expected to increase to 80 million per year by 2040.
The median age of the world's population was estimated to be 30.4 years in 2018.
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