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Demography (from prefix ''demo-'' from
Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period (), and the period (). Ancient Greek was the language of an ...
δῆμος (''dēmos'') meaning 'the people', and ''-graphy'' from γράφω (''graphō'') meaning 'writing, description or measurement') is the
statistical study A statistical hypothesis is a hypothesis that is testable on the basis of Observable variable, observed data statistical model, modelled as the realised values taken by a collection of random variables. A set of data is modelled as being realised ...

statistical study
of
population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ...

population
s, especially
human beings Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and large, complex brains. This has enabled the development of advanced tools, culture, and language. Humans are highly ...

human beings
.
Demographic analysis Demographic analysis includes the things that allow us to measure the dimensions and dynamics Dynamics (from Greek language, Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' "power (disambiguation), power") or dy ...
can cover whole societies or groups defined by criteria such as
education Education is the process of facilitating , or the acquisition of , s, , morals, s, s, and personal development. Educational methods include , , , and directed . Education frequently takes place under the guidance of educators; however, lea ...

education
,
nationality Nationality is a legal identification of a person in international law International law, also known as public international law and law of nations, is the set of rules, norms, and standards generally accepted in relations between nations. I ...
,
religion Religion is a - of designated and practices, , s, s, , , , , or , that relates humanity to , , and elements; however, there is no scholarly consensus over what precisely constitutes a religion. Different religions may or may not contain v ...

religion
, and
ethnicity An ethnic group or ethnicity is a grouping of people who identity (social science), identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancest ...

ethnicity
. Educational institutions usually treat demography as a field of
sociology Sociology is a social science Social science is the Branches of science, branch of science devoted to the study of society, societies and the Social relation, relationships among individuals within those societies. The term was formerly ...
, though there are a number of independent demography departments. Patient demographics form the core of the data for any medical institution, such as patient and emergency contact information and patient medical record data. They allow for the identification of a patient and his categorization into categories for the purpose of statistical analysis. Patient demographics include:
Date of birth A birthday is the anniversary An anniversary is the date on which an event took place or an institution was founded in a previous year, and may also refer to the commemoration or celebration of that event. For example, the first event is ...
,
gender Gender is the range of characteristics pertaining to, and differentiating between femininity Femininity (also called womanliness or girlishness) is a set of attributes, behaviors, and roles generally associated with women and girls. Althoug ...

gender
(Ref: Google Health), Date of
death Death is the permanent, irreversible cessation of all biological functions that sustain a living Living or The Living may refer to: Common meanings *Life, a condition that distinguishes organisms from inorganic objects and dead organi ...

death
, postal code,
ethnicity An ethnic group or ethnicity is a grouping of people who identity (social science), identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancest ...

ethnicity
,
blood type A blood type (also known as a blood group) is a classification of , based on the presence and absence of and ic substances on the surface of s (RBCs). These antigens may be s, s, s, or s, depending on the blood group system. Some of these anti ...
(Ref: Microsoft HealthVault: Personal Demographic Information, Basic Demographic Information), Emergency contact information, family doctor, insurance provider data,
Allergies Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, i ...

Allergies
, major diagnoses and major medical history. 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.


History

Demographic thoughts traced back to antiquity, and were present in many civilisations and cultures, like
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era wa ...
,
Ancient Rome In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived in the 5th century BC and one of the earliest historians whose work survives. A historian is a person who stud ...
,
China China (), officially the People's Republic of China (PRC; ), is a country in . It is the world's , with a of more than 1.4 billion. China spans five geographical and 14 different countries, the in the world after . Covering an area of ap ...

China
and
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

India
.S.C.Srivastava,''Studies in Demography'', p.39-41
/ref> Made up of the prefix ''demo-'' and the suffix ''-graphy'', the term Demography refers to the overall study of population. In ancient Greece, this can be found in the writings of
Herodotus Herodotus ( ; grc, Ἡρόδοτος, Hēródotos, ; BC) was an ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), ge ...
,
Thucidides Thucydides (; grc-gre, Θουκυδίδης ; BC) was an Athenian , image_skyline = File:Athens Montage L.png, center, 275px, alt=Athens montage. Clicking on an image in the picture causes the browser to load the app ...
,
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as , was a of the (), who is considered one of the most outstanding figures in the . He is traditionally referred to as the "Father of ...

Hippocrates
,
Epicurus Epicurus, ''Epíkouros'', "ally, comrade" (341–270 BC) was an and who founded , a highly influential school of . He was born on the Greek island of to parents. Influenced by , , , and possibly the , he turned against the of his day and e ...

Epicurus
,
Protagoras Protagoras (; el, Πρωταγόρας; )Guthrie, p. 262–263. was a pre-Socratic Pre-Socratic philosophy is ancient Greek philosophy Ancient Greek philosophy arose in the 6th century BC, at a time when the inhabitants of ancient Greece wer ...
,
Polus Polus (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...

Polus
,
Plato Plato ( ; grc-gre, wikt:Πλάτων, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was an Classical Athens, Athenian philosopher during the Classical Greece, Classical period in Ancient Greece, founder of the Platonist school of thoug ...

Plato
and
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental quest ...

Aristotle
. In Rome, writers and philosophers like
Cicero Marcus Tullius Cicero ( ; ; 3 January 106 BC – 7 December 43 BC) was a Ancient Rome, Roman statesman, lawyer, scholar, philosopher and Academic skepticism, Academic Skeptic, who tried to uphold optimate principles during crisis of ...

Cicero
,
Seneca Seneca may refer to: People and language *Seneca (name), a list of people with either the given name or surname *Seneca the Elder, a Roman rhetorician, writer and father of the stoic philosopher Seneca the Younger *Seneca the Younger, a Roman Stoi ...
,
Pliny the elder #REDIRECT Pliny the Elder#REDIRECT Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, a naturalist Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, ...

Pliny the elder
,
Marcus Aurelius Marcus Aurelius Antoninus ( ; 26 April 121 – 17 March 180) was a Roman emperor from 161 to 180 and a Stoicism, Stoic philosopher. He was the last of the rulers known as the Five Good Emperors (a term coined some 13 centuries later by Nicc ...

Marcus Aurelius
,
Epictetus Epictetus (; grc-gre, Ἐπίκτητος, ''Epíktētos''; 50 135 AD) was a Greek Stoic philosopher. He was born into slavery at Hierapolis Hierapolis ( grc, Ἱεράπολις, lit. "Holy City") was an ancient Greek city located on ho ...

Epictetus
,
Cato Cato typically refers to either Cato the Elder or Cato the Younger, both of the Porcii Catones family of Rome. It may also refer to any of the following: People Romans, in the family Porcii Catones * Cato the Elder (Cato Maior) or "the Censor" ...
, and
Columella Lucius Junius Moderatus Columella (; Arabic: Yunius, 4 – c. 70 AD) was a prominent writer on agriculture in the Roman empire. His ''De re rustica'' in twelve volumes has been completely preserved and forms an important source on Roman agri ...
also expressed important ideas on this ground. In the
Middle ages In the history of Europe The history of Europe concerns itself with the discovery and collection, the study, organization and presentation and the interpretation of past events and affairs of the people of Europe since the beginning of ...
, Christian thinkers devoted much time in refuting the Classical ideas on demography. Important contributors to the field were
William of Conches William of Conches (c. 1090/1091 – c. 1155/1170s) was a French people, French Scholasticism, scholastic philosopher who sought to expand the bounds of Christian humanism by studying secular works of the classics and fostering empirical science ...
,Peter Biller,''The measure of multitude: Population in medieval thought

Bartholomew of Lucca Bartholomew of Lucca, born Bartolomeo Fiadoni, and also known as Tolomeo da Lucca or Ptolemy da Lucca (c. 1236 – c. 1327), was a medieval Italian historian. Biography Born in Lucca, probably in 1236, at an early age Bartholomew entered th ...
,
William of Auvergne Image:Guillaume - Opere, 1674 - 4420357 F.tif, ''Opera omnia'', 1674 William of Auvergne (1180/90–1249) was a France, French theologian and philosopher who served as Bishop of Paris from 1228 until his death. He was one of the first western Euro ...
, William of Pagula, and Muslim sociologists like
Ibn Khaldun Ibn Khaldun (; ar, أبو زيد عبد الرحمن بن محمد بن خلدون الحضرمي, ; 27 May 1332 – 17 March 1406) was an Arab The Arabs (singular Arab ; singular ar, عَرَبِيٌّ, : , Arabic pronunciation: , plural ...
. One of the earliest demographic studies in the modern period was ''Natural and Political Observations Made upon the Bills of Mortality'' (1662) by
John Graunt John Graunt (24 April 1620 – 18 April 1674) has been regarded as the founder of demography Demography (from prefix ''demo-'' from Ancient Greek δῆμος (''dēmos'') meaning 'the people', and ''-graphy'' from γράφω (''graphō'') m ...
, which contains a primitive form of
life table In actuarial science 2003 US mortality ( life) table, Table 1, Page 1 Actuarial science is the discipline that applies mathematical Mathematics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( ...
. Among the study's findings were that one-third of the children in London died before their sixteenth birthday. Mathematicians, such as
Edmond Halley Edmond (or Edmund) Halley (; – ) was an English astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such ...

Edmond Halley
, developed the life table as the basis for life insurance mathematics.
Richard Price Richard Price (23 February 1723 – 19 April 1791) was a Welsh moral philosopher, Nonconformist minister and mathematician. He was also a political reformer, pamphleteer, active in radical, republican, and liberal causes such as the French a ...

Richard Price
was credited with the first textbook on life contingencies published in 1771, followed later by
Augustus de Morgan Augustus De Morgan (27 June 1806 – 18 March 1871) was a British mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), f ...

Augustus de Morgan
, ‘On the Application of Probabilities to Life Contingencies’ (1838). In 1755,
Benjamin Franklin Benjamin Franklin ( April 17, 1790) was one of the Founding Fathers of the United States that was negotiated on behalf of the United States by John Adams, Benjamin Franklin and John Jay The Founding Fathers of the United States, or simp ...

Benjamin Franklin
published his essay '' Observations Concerning the Increase of Mankind, Peopling of Countries, etc.'', projecting
exponential growth Exponential growth is a process that increases quantity over time. It occurs when the instantaneous Rate (mathematics)#Of change, rate of change (that is, the derivative) of a quantity with respect to time is proportionality (mathematics), proport ...

exponential growth
in British colonies. His work influenced
Thomas Robert Malthus Thomas Robert Malthus (; 13/14 February 1766 – 23 December 1834) was an English cleric, scholar and influential economist in the fields of political economy and demography. In his 1798 book ''An Essay on the Principle of Population The ...

Thomas Robert Malthus
, who, writing at the end of the 18th century, feared that, if unchecked, population growth would tend to outstrip growth in food production, leading to ever-increasing famine and poverty (see
Malthusian catastrophe Malthusianism is the idea that population growth is potentially exponential while the growth of the food supply or other resources is linear growth, linear, which eventually reduces living standards to the point of triggering a depopulation, popula ...
). Malthus is seen as the intellectual father of ideas of
overpopulation Overpopulation or overabundance occurs when a species' population In biology, a population is a number of all the organisms of the same group or species In biology, a species is the basic unit of biological classification, classifica ...
and the limits to growth. Later, more sophisticated and realistic models were presented by
Benjamin Gompertz Benjamin Gompertz (5 March 1779 – 14 July 1865) was a British self-educated Autodidacticism (also autodidactism) or self-education (also self-learning and self-teaching) is education Education is the process of facilitating lea ...
and Verhulst. In 1855, a Belgian scholar Achille Guillard defined demography as the natural and social history of human species or the mathematical knowledge of populations, of their general changes, and of their physical, civil, intellectual, and moral condition. The period 1860-1910 can be characterized as a period of transition where in demography emerged from statistics as a separate field of interest. This period included a panoply of international ‘great demographers’ like Adolphe Quételet (1796–1874),
William Farr William Farr CB (30 November 1807 – 14 April 1883) was a British epidemiologist, regarded as one of the founders of medical statistics. Early life He was born in Kenley, Shropshire, to poor parents. He was effectively adopted by a local squi ...

William Farr
(1807–1883),
Louis-Adolphe Bertillon Louis-Adolphe Bertillon (; 1 April 1821 in Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents as of 2018, ...
(1821–1883) and his son
Jacques Ancient and noble French family names, Jacq, Jacques, or James are believed to originate from the Middle Ages in the historic northwest Brittany region in France France (), officially the French Republic (french: link=no, République fran ...

Jacques
(1851–1922), Joseph Körösi (1844–1906), Anders Nicolas Kaier (1838–1919), Richard Böckh (1824–1907),
Émile Durkheim David Émile Durkheim ( or ; 15 April 1858 – 15 November 1917) was a French sociologist. He formally established the academic discipline of sociology and, with Max Weber Maximilian Karl Emil Weber (; ; 21 April 186414 June 1920) was a Ge ...

Émile Durkheim
(1858-1917), Wilhelm Lexis (1837–1914), and Luigi Bodio (1840–1920) contributed to the development of demography and to the toolkit of methods and techniques of demographic analysis.


Methods

There are two types of data collection—direct and indirect—with several different methods of each type.


Direct methods

Direct data comes from vital statistics registries that track all births and deaths as well as certain changes in legal status such as marriage, divorce, and migration (registration of place of residence). In developed countries with good registration systems (such as the United States and much of Europe), registry statistics are the best method for estimating the number of births and deaths. A
census A census is the procedure of systematically calculating, acquiring and recording information Information is processed, organised and structured data Data (; ) are individual facts, statistics, or items of information, often numeric. In ...

census
is the other common direct method of collecting demographic data. A census is usually conducted by a national government and attempts to enumerate every person in a country. In contrast to vital statistics data, which are typically collected continuously and summarized on an annual basis, censuses typically occur only every 10 years or so, and thus are not usually the best source of data on births and deaths. Analyses are conducted after a census to estimate how much over or undercounting took place. These compare the
sex ratio The sex ratio is the ratio In mathematics, a ratio indicates how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8 ...
s from the census data to those estimated from natural values and mortality data. Censuses do more than just count people. They typically collect information about families or households in addition to individual characteristics such as age, sex, marital status, literacy/education, employment status, and occupation, and geographical location. They may also collect data on migration (or place of birth or of previous residence), language, religion, nationality (or ethnicity or race), and citizenship. In countries in which the vital registration system may be incomplete, the censuses are also used as a direct source of information about fertility and mortality; for example the censuses of the
People's Republic of China China (), officially the People's Republic of China (PRC; ), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere ...

People's Republic of China
gather information on births and deaths that occurred in the 18 months immediately preceding the census.


Indirect methods

Indirect methods of collecting data are required in countries and periods where full data are not available, such as is the case in much of the developing world, and most of
historical demography Historical demography is the quantitative study of human population in the past. It is concerned with population size, with the three basic components of population change-- fertility, mortality, and migration, and with population characterist ...
. One of these techniques in contemporary demography is the sister method, where survey researchers ask women how many of their sisters have died or had children and at what age. With these surveys, researchers can then indirectly estimate birth or death rates for the entire population. Other indirect methods in contemporary demography include asking people about siblings, parents, and children. Other indirect methods are necessary in historical demography. There are a variety of demographic methods for modelling population processes. They include models of mortality (including the
life table In actuarial science 2003 US mortality ( life) table, Table 1, Page 1 Actuarial science is the discipline that applies mathematical Mathematics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( ...
, Gompertz models, hazards models, Cox proportional hazards models, multiple decrement life tables,
Brass relational logits Brass is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appear ...
),
fertility Fertility is the capability to produce through following the onset of . The is the average number of children born by a female during her lifetime and is quantified . Fertility is addressed when there is a difficulty or an inability to repro ...
(
Hernes modelHernes is a surname. Notable people with the surname include: *Gudmund Hernes (born 1941), Norwegian politician * Helga Hernes (born 1938), German-born Norwegian political scientist, diplomat, and politician See also

*Herne (disambiguation) {{ ...
, Coale-Trussell models, parity progression ratios), marriage (Singulate Mean at Marriage,
Page model Page most commonly refers to: * Page (paper) A page is one side of a leaf A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. Th ...
), disability ( Sullivan's method, multistate life tables), population projections ( Lee-Carter model, the Leslie Matrix), and
population momentumPopulation momentum is a consequence of the demographic transition. Population momentum explains why a population In biology, a population is a number of all the organisms of the same group or species In biology, a species is the basic ...
( Keyfitz). The United Kingdom has a series of four national birth cohort studies, the first three spaced apart by 12 years: the 1946 National Survey of Health and Development, the 1958
National Child Development StudyThe National Child Development Study (NCDS) is a continuing, multi-disciplinary longitudinal study A longitudinal study (or longitudinal survey, or panel study) is a research design that involves repeated observations of the same variables (e.g., pe ...
, the
1970 British Cohort StudyThe 1970 British Cohort Study (BCS70) is a continuing, multi-disciplinary longitudinal survey monitoring the development of babies born in the UK during the week of 5–11 April 1970. History Since the start of the BCS70, eight full sets of data ha ...
, and the Millennium Cohort Study, begun much more recently in 2000. These have followed the lives of samples of people (typically beginning with around 17,000 in each study) for many years, and are still continuing. As the samples have been drawn in a nationally representative way, inferences can be drawn from these studies about the differences between four distinct generations of British people in terms of their health, education, attitudes, childbearing and employment patterns.


Common rates and ratios

* The crude
birth rate The crude birth rate (CBR) in a period is the total number of live births per 1,000 population divided by the length of the period in years. The number of live births is normally taken from a universal registration system for births; population ...
, the annual number of live births per 1,000 people. * The general
fertility rate The total fertility rate (TFR) of a population is the average number of children that would be born to a woman over her lifetime if: # she was to experience the exact current age-specific rates (ASFRs) through her lifetime # she was to live from ...

fertility rate
, the annual number of live births per 1,000 women of childbearing age (often taken to be from 15 to 49 years old, but sometimes from 15 to 44). * The age-specific fertility rates, the annual number of live births per 1,000 women in particular age groups (usually age 15–19, 20-24 etc.) * The crude
death rate Mortality rate, or death rate, is a measure of the number of death (1906) Death is the permanent, Irreversible process, irreversible cessation of all biological process, biological functions that sustain a living organism. Brain death is ...
, the annual number of deaths per 1,000 people. * The
infant mortality rate Infant mortality is the death of young children under the age of 1. This death toll is measured by the infant mortality rate (IMR), which is the probability of deaths of children under one year of age per 1000 live births. The under-five mortalit ...
, the annual number of deaths of children less than 1 year old per 1,000 live births. * The expectation of life (or
life expectancy Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of its birth, its current age, and other demographic Demography (from prefix ''demo-'' from Ancient Greek Ancien ...

life expectancy
), the number of years that an individual at a given age could expect to live at present mortality levels. * The total fertility rate, the number of live births per woman completing her reproductive life, if her childbearing at each age reflected current age-specific fertility rates. * The replacement level fertility, the average number of children women must have in order to replace the population for the next generation. For example, the replacement level fertility in the US is 2.11.Introduction to environmental engineering and science by Masters and Ela, 2008, Pearson Education, chapter 3 * The gross reproduction rate, the number of daughters who would be born to a woman completing her reproductive life at current age-specific fertility rates. * The net reproduction ratio is the expected number of daughters, per newborn prospective mother, who may or may not survive to and through the ages of childbearing. * A stable population, one that has had constant crude birth and death rates for such a long period of time that the percentage of people in every age class remains constant, or equivalently, the population pyramid has an unchanging structure. * A stationary population, one that is both stable and unchanging in size (the difference between crude birth rate and crude death rate is zero). A stable population does not necessarily remain fixed in size. It can be expanding or shrinking. Note that the crude death rate as defined above and applied to a whole population can give a misleading impression. For example, the number of deaths per 1,000 people can be higher for developed nations than in less-developed countries, despite standards of health being better in developed countries. This is because developed countries have proportionally more older people, who are more likely to die in a given year, so that the overall mortality rate can be higher even if the mortality rate at any given age is lower. A more complete picture of mortality is given by a
life table In actuarial science 2003 US mortality ( life) table, Table 1, Page 1 Actuarial science is the discipline that applies mathematical Mathematics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( ...
, which summarizes mortality separately at each age. A life table is necessary to give a good estimate of life expectancy.


Basic equation regarding development of a population

Suppose that a country (or other entity) contains ''Populationt'' persons at time ''t''. What is the size of the population at time ''t'' + 1 ? :\text_ = \text_t + \text_t + \text_t Natural increase from time ''t'' to ''t'' + 1: :\text_t = \text_t - \text_t Net migration from time ''t'' to ''t'' + 1: :\text_t = \text_t - \text_t These basic equations can also be applied to subpopulations. For example, the population size of ethnic groups or nationalities within a given society or country is subject to the same sources of change. When dealing with ethnic groups, however, "net migration" might have to be subdivided into physical migration and ethnic reidentification ( assimilation). Individuals who change their ethnic self-labels or whose ethnic classification in government statistics changes over time may be thought of as migrating or moving from one population subcategory to another. More generally, while the basic demographic equation holds true by definition, in practice the recording and counting of events (births, deaths, immigration, emigration) and the enumeration of the total population size are subject to error. So allowance needs to be made for error in the underlying statistics when any accounting of population size or change is made. The figure in this section shows the latest (2004) UN projections of world population out to the year 2150 (red = high, orange = medium, green = low). The UN "medium" projection shows world population reaching an approximate equilibrium at 9 billion by 2075. Working independently, demographers at the
International Institute for Applied Systems Analysis The International Institute for Applied Systems Analysis (IIASA) is an independent international research institute located in Laxenburg, near Vienna en, Viennese , iso_code = AT-9 , registration_plate ...
in Austria expect world population to peak at 9 billion by 2070. Throughout the 21st century, the average age of the population is likely to continue to rise.


Science of population

Populations can change through three processes: fertility, mortality, and migration. Fertility involves the number of children that women have and is to be contrasted with fecundity (a woman's childbearing potential). Mortality is the study of the causes, consequences, and measurement of processes affecting death to members of the population. Demographers most commonly study mortality using the
Life Table In actuarial science 2003 US mortality ( life) table, Table 1, Page 1 Actuarial science is the discipline that applies mathematical Mathematics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( ...
, a statistical device that provides information about the mortality conditions (most notably the life expectancy) in the population. Migration refers to the movement of persons from a locality of origin to a destination place across some predefined, political boundary. Migration researchers do not designate movements 'migrations' unless they are somewhat permanent. Thus demographers do not consider tourists and travellers to be migrating. While demographers who study migration typically do so through census data on place of residence, indirect sources of data including tax forms and labour force surveys are also important. Demography is today widely taught in many universities across the world, attracting students with initial training in social sciences, statistics or health studies. Being at the crossroads of several disciplines such as
sociology Sociology is a social science Social science is the Branches of science, branch of science devoted to the study of society, societies and the Social relation, relationships among individuals within those societies. The term was formerly ...
,
economics Economics () is a social science Social science is the branch A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science of plant life and a bran ...

economics
,
epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants In mathematics, the determinant is a Scalar (mathematics), scalar value that is a function (mathematics), function of the entries of a ...
,
geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10. ...

geography
,
anthropology Anthropology is the scientific study of human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natural science that studies life and living organisms, including their anatomy, ...
and
history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

history
, demography offers tools to approach a large range of population issues by combining a more technical quantitative approach that represents the core of the discipline with many other methods borrowed from social or other sciences. Demographic research is conducted in universities, in research institutes as well as in statistical departments and in several international agencies. Population institutions are part of the
Cicred The Committee for International Cooperation in National Research in Demography, commonly known as CICRED, is a accredited with the of the . Founded in 1972, it aims at developing cooperation amongst national population centres, and encouraging ne ...
(International Committee for Coordination of Demographic Research) network while most individual scientists engaged in demographic research are members of the International Union for the Scientific Study of Population, or a national association such as the Population Association of America in the United States, or affiliates of the Federation of Canadian Demographers in Canada.Canadian Population Society


See also

* Biodemography *Biodemography of human longevity * Demographics of the world * Demographic economics * Gompertz–Makeham law of mortality * Linguistic demography * List of demographics articles * Medieval demography * National Security Study Memorandum 200 of 1974 * NRS social grade * Political demography * Population biology * Population dynamics * Population geography * Population reconstruction * Population statistics * Religious demography * Replacement migration * Reproductive health


Social surveys

* Current Population Survey (CPS) * Demographic and Health Surveys (DHS) * European Social Survey (ESS) * General Social Survey (GSS) * German General Social Survey (ALLBUS) * Multiple Indicator Cluster Surveys (MICS) * National Longitudinal Survey (NLS) * Panel Study of Income Dynamics (PSID) * PMA2020, Performance Monitoring and Accountability 2020 (PMA2020) * Socio-Economic Panel (SOEP, German) * World Values Survey (WVS)


Organizations

* Global Social Change Research Project (United States) * Institut national d'études démographiques (INED) (France) * Max Planck Institute for Demographic Research (Germany) * Office of Population Research (Princeton University) (United States) * Population Council (United States) * Population Studies Center at the University of Michigan (United States) * Vienna Institute of Demography (VID) (Austria) * Wittgenstein Centre for Demography and Global Human Capital (Austria)


Scientific journals

* ''Brazilian Journal of Population Studies'' * ''Cahiers québécois de démographie'' * ''Demography (journal), Demography'' * ''Population and Development Review''


References


Further reading

* Josef Ehmer, Jens Ehrhardt, Martin Kohli (Eds.)
''Fertility in the History of the 20th Century: Trends, Theories, Policies, Discourses''
Historical Social Research 36 (2), 2011. * Glad, John. 2008.
Future Human Evolution: Eugenics in the Twenty-First Century
'. Hermitage Publishers, * Gavrilova N.S., Gavrilov L.A. 2011. Ageing and Longevity: Mortality Laws and Mortality Forecasts for Ageing Populations [In Czech: Stárnutí a dlouhověkost: Zákony a prognózy úmrtnosti pro stárnoucí populace]. Demografie, 53(2): 109–128. * Preston, Samuel, Patrick Heuveline, and Michel Guillot. 2000. ''Demography: Measuring and Modeling Population Processes''. Blackwell Publishing. * Gavrilov L.A., Gavrilova N.S. 2010. Demographic Consequences of Defeating Aging. Rejuvenation Research, 13(2-3): 329–334. * Paul R. Ehrlich (1968), ''The Population Bomb'' Controversial Neo-Malthusianist pamphlet * Leonid A. Gavrilov & Natalia S. Gavrilova (1991), ''The Biology of Life Span: A Quantitative Approach''. New York: Harwood Academic Publisher, * Uhlenberg P. (Editor), (2009) International Handbook of the Demography of Aging, New York: Springer-Verlag, pp. 113–131. * Paul Demeny and Geoffrey McNicoll (Eds.). 2003. The Encyclopedia of Population. New York, Macmillan Reference USA, vol.1, 32-37 * Phillip Longman (2004), ''The Empty Cradle: how falling birth rates threaten global prosperity and what to do about it'' * Sven Kunisch, Stephan A. Boehm, Michael Boppel (eds) (2011). ''From Grey to Silver: Managing the Demographic Change Successfully'', Springer-Verlag, Berlin Heidelberg, * Joe McFalls (2007),
Population: A Lively Introduction
'' Population Reference Bureau * Ben J. Wattenberg (2004), ''How the New Demography of Depopulation Will Shape Our Future''. Chicago: R. Dee,


External links


Quick demography data lookup
*
Historicalstatistics.org
Links to historical demographic and economic statistics

*

Population estimates and projections for 230 countries and areas *

Estimates and projections of urban and rural populations and urban agglomerations *

Probabilistic Population Projections, based on the 2010 Revision of the World Population Prospects.



* [http://gsociology.icaap.org/report/demsum.html Brief review of world basic demographic trends]
Family and Fertility Surveys
(FFS)
Population Division
(DESA) (United Nations) {{Authority control Demography, Actuarial science Environmental social science Interdisciplinary subfields of sociology Human geography Market segmentation Human populations