The Demography of the World Population from 1950 to 2100. Data source: United Nations — World Population Prospects 2017
Demography (from Ancient Greekδῆμος (dêmos)'people, society' and -γραφία (-graphía)'writing, drawing, description')[1] is thestatistical study of humanpopulations: their size, composition (e.g., ethnic group, age), and how they change through the interplay of fertility (births), mortality (deaths), and migration.[2]
Demographic analysis examines and measures the dimensions anddynamics of populations; it can cover whole societies or groups defined by criteria such aseducation,nationality,religion, andethnicity. Educational institutions[3] usually treat demography as a field ofsociology, though there are a number of independent demography departments.[4] These methods have primarily been developed to study human populations, but are extended to a variety of areas where researchers want to know how populations ofsocial actors can change across time through processes of birth, death, andmigration. In the context ofhuman biological populations, demographic analysis usesadministrative records to develop an independentestimate of the population.[5]Demographic analysis estimates are often considered a reliable standard for judging the accuracy of thecensus information gathered at any time. In thelabor force, demographic analysis is used to estimate sizes and flows of populations of workers; inpopulation ecology the focus is on the birth, death, migration and immigration of individuals in a population of living organisms, alternatively, in social human sciences could involve movement of firms andinstitutional forms. Demographic analysis is used in a wide variety of contexts. For example, it is often used in business plans, to describe the population connected to the geographic location of the business.[6] Demographic analysis is usually abbreviated as DA.[7] For the 2010 U.S. Census, TheU.S. Census Bureau has expanded its DA categories.[7] Also as part of the 2010 U.S. Census, DA now also includes comparative analysis between independent housing estimates, and census address lists at different key time points.[7]
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 their categorization into categories for the purpose of statistical analysis. Patient demographics include:date of birth,gender, date ofdeath, postal code, ethnicity,blood type, emergency contact information, family doctor, insurance provider data,allergies, major diagnoses and major medical history.[8]
Formal demography limits its object of study to the measurement of population processes, while the broader field ofsocial demography or population studies also analyses the relationships between economic, social, institutional, cultural, and biological processes influencing a population.[9]
Demographic thoughts traced back to antiquity, and were present in many civilisations and cultures, likeAncient Greece,Ancient Rome,China andIndia.[10] Made up of the prefixdemo- and the suffix-graphy, the termdemography refers to the overall study of population.[11]
One of the earliest demographic studies in the modern period wasNatural and Political Observations Made upon the Bills of Mortality (1662) byJohn Graunt, which contains a primitive form oflife table. Among the study's findings were that one-third of the children inLondon died before their sixteenth birthday. Mathematicians, such asEdmond Halley, developed the life table as the basis for life insurance mathematics.Richard Price was credited with the first textbook on life contingencies published in 1771,[14] followed later byAugustus De Morgan,On the Application of Probabilities to Life Contingencies (1838).[15]
In 1855, aBelgian 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.[18]
Newell (1988, p. 4-5) claims that the first major developments in the 20th century, in what was to become formal demography, were made in three papers byAlfred J. Lotka (1907, 1911 (with F.R. Sharpe) and 1922 where a Stable Population Model was developed. This model was similar toLeonhard Euler's earlier but overlooked modelling which showed how a population with constant fertility and mortality might grow geometrically using a difference equation. Under this geometric growth Euler also examined relationships among various demographic indices showing how they might be used to produce estimates when data was missing. Lotka (and Sharpe) showed that a closed population (assuming constant both age-specific mortality and fertility) developed along a path leading to a fixed age structure - The Stable Population.[19][20][21][22][23]
Early censuses and surveys provided demographic data.
Demography is thestatistical and mathematical study of the size, composition, andspatial distribution of human populations and how these features change over time. Data are obtained from a census of the population and from registries: records of events likebirth,deaths, migrations, marriages,divorces, diseases, andemployment. To do this, there needs to be an understanding of how they are calculated and the questions they answer which are included in these four concepts:population change,standardization of population numbers, the demographic bookkeeping equation, and population composition.[citation needed]
There are two types ofdata collection—direct and indirect—with several methods of each type.
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 theUnited States and much ofEurope), registry statistics are the best method for estimating the number of births and deaths.
Acensus 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 thesex ratios 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 thePeople's Republic of China gather information on births and deaths that occurred in the 18 months immediately preceding the census.
Map ofcountries by populationRate of human population growth showing projections for later this century[24]
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 ofhistorical demography. 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.[citation needed]
The United Kingdom has a series of four national birth cohort studies, the first three spaced apart by 12 years: the1946 National Survey of Health and Development, the 1958National Child Development Study,[25] the1970 British Cohort Study,[26] and theMillennium 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.[27]
Indirect standardization is used when a population is small enough that the number of events (births, deaths, etc.) are also small. In this case, methods must be used to produce a standardizedmortality rate (SMR) or standardized incidence rate (SIR).[28][29]
Population change is analyzed by measuring the change between one population size to another.Global population continues to rise, which makes population change an essential component to demographics. This is calculated by taking one population size minus the population size in an earliercensus. The best way of measuring population change is using the intercensal percentage change. The intercensal percentage change is the absolute change in population between the censuses divided by the population size in the earlier census. Next, multiply this a hundredfold to receive apercentage. When this statistic is achieved, thepopulation growth between two or morenations that differ in size, can be accurately measured and examined.[30][31]
For there to be asignificant comparison, numbers must be altered for the size of the population that is under study. For example, thefertility rate is calculated as the ratio of the number of births to women of childbearing age to the total number of women in this age range. If these adjustments were not made, we would not know if a nation with a higher rate of births or deaths has a population with more women of childbearing age or more births per eligible woman.[citation needed]
Within the category ofstandardization, there are two major approaches: direct standardization and indirect standardization.[32]
Thecrudebirth rate, the annual number of live births per 1,000 people.
Thegeneralfertility 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).
Theage-specific fertility rates, the annual number of live births per 1,000 women in particular age groups (usually age 15–19, 20–24 etc.)
Thecrudedeath rate, the annual number of deaths per 1,000 people.
Theinfant mortality rate, the annual number of deaths of children less than 1 year old per 1,000 live births.
Theexpectation of life (orlife expectancy), the number of years that an individual at a given age could expect to live at present mortality levels.
Thetotal 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.
Thereplacement 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.[33]
Thegross reproduction rate, the number of daughters who would be born to a woman completing her reproductive life at current age-specific fertility rates.
Thenet 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.
Astable 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, thepopulation pyramid has an unchanging structure.[33]
Astationary population, one that is both stable and unchanging in size (the difference between crude birth rate and crude death rate is zero).[33]
Measures of centralisation are concerned with the extent to which an area's population is concentrated in itsurban centres.[34][35]
A stable population does not necessarily remain fixed in size. It can be expanding or shrinking.[33]
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 in 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 alife table, 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
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.[36]
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 (United Nations)WHO projections ofworld 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 theInternational Institute for Applied Systems Analysis inAustria expect world population to peak at 9 billion by 2070.[37] Throughout the 21st century, the average age of the population is likely to continue to rise.
Populations can change through three processes: fertility, mortality, and migration. Fertility involves the number of children that women have and is to be contrasted withfecundity (a woman's childbearing potential).[38] 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 thelife table, a statistical device that provides information about the mortality conditions (most notably the life expectancy) in the population.[39]
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.[40]
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 associology,economics,epidemiology,geography,anthropology andhistory, 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 theCICRED (International Committee for Coordination of Demographic Research) network while most individual scientists engaged in demographic research are members of theInternational Union for the Scientific Study of Population,[41] or a national association such as thePopulation Association of America in the United States,[42] or affiliates of the Federation of Canadian Demographers inCanada.[43]
World demography by age composition from 1950 to 2100 (projected).[44]
Population composition is the description of population defined by characteristics such as age,race, sex ormarital status. These descriptions can be necessary for understanding thesocial dynamics from historical and comparative research. This data is often compared using apopulation pyramid.
Population composition is also a very important part of historical research. Information ranging back hundreds of years is not always worthwhile, because the numbers of people for which data are available may not provide the information that is important (such aspopulation size). Lack of information on the original data-collection procedures may prevent accurate evaluation of data quality.
Demographic analysis in institutions and organizations
The demographic analysis oflabor markets can be used to show slow population growth,population ageing, and the increased importance of immigration. The U.S. Census Bureau projects that in the next 100 years, the United States will face some dramatic demographic changes.[citation needed] The population is expected to grow more slowly and age more rapidly than ever before and the nation will become a nation of immigrants. This influx is projected to rise over the next century as new immigrants and their children will account for over half the U.S. population. These demographic shifts could ignite major adjustments in the economy, more specifically, in labor markets.[citation needed]
People decide to exit organizations for many reasons, such as, better jobs, dissatisfaction, and concerns within the family. The causes of turnover can be split into two separate factors, one linked with the culture of the organization, and the other relating to all other factors. People who do not fully accept a culture might leave voluntarily. Or, some individuals might leave because they fail to fit in and fail to change within a particular organization.
A basic definition of population ecology is a study of the distribution and abundance of organisms. As it relates to organizations and demography, organizations go through variousliabilities to their continued survival. Hospitals, like all other large and complex organizations are impacted in the environment they work. For example, a study was done on the closure of acute care hospitals in Florida between a particular time. The study examined effect size, age, and niche density of these particular hospitals. A population theory says that organizational outcomes are mostly determined byenvironmental factors. Among several factors of the theory, there are four that apply to the hospital closure example: size, age, density of niches in which organizations operate, and density of niches in which organizations are established.[citation needed]
Problems in which demographers may be called upon to assist business organizations are when determining the best prospective location in an area of a branch store or service outlet, predicting the demand for a new product, and to analyze certain dynamics of a company's workforce. Choosing a new location for a branch of a bank, choosing the area in which to start a new supermarket, consulting a bankloan officer that a particular location would be a beneficial site to start a car wash, and determining what shopping area would be best to buy and be redeveloped in metropolis area are types of problems in which demographers can be called upon.
Standardization is a useful demographic technique used in the analysis of a business. It can be used as an interpretive and analytic tool for the comparison of different markets.
These organizations have interests about the number and characteristics of their clients so they can maximize the sale of their products, their outlook on their influence, or the ends of their power, services, and beneficial works.
^abcUS Census Bureau Webdesign: SSD, Laura K Yax, Content: DSSD, Phil Gbur, POP, Jason Devine."Coverage Measurement".Archived from the original on 10 January 2016. Retrieved26 March 2016.{{cite web}}: CS1 maint: multiple names: authors list (link)
^"Our Yesterdays: the History of the Actuarial Profession in North America, 1809-1979," by E.J. (Jack) Moorhead, FSA, (1/23/10 – 2/21/04), published by the Society of Actuaries as part of the profession's centennial celebration in 1989.
^The History of Insurance, Vol 3, Edited by David Jenkins and Takau Yoneyama (1 85196 527 0): 8 Volume Set: (2000) Availability: Japan: Kinokuniya).
^Caves, R. W. (2004).Encyclopedia of the City. Routledge. p. 169.
^Newell, Colin. (1988) Methods and models in demography. Belhaven Press.
^Inaba, Hisashi (2017) Chapter 1 The Stable Population Model inAge-structured population dynamics in demography and epidemiology. Springer Singapore.
^Lotka, A. J. (1907). Relation between birth rates and death rates. Science, 26(653), 21-22.
^Sharpe, F. R., & Lotka, A. J. (1911). L. A problem in age-distribution. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 21(124), 435-438.
^Lotka, A. J. (1922). The stability of the normal age distribution. Proceedings of the National Academy of Sciences, 8(11), 339-345.
^See, for example, Barbara A. Anderson and Brian D. Silver, "Estimating Russification of Ethnic Identity Among Non-Russians in the USSR,"Demography, Vol. 20, No. 4 (Nov., 1983): 461–489.
^John Bongaarts. The Fertility-Inhibiting Effects of the Intermediate Fertility Variables. Studies in Family Planning, Vol. 13, No. 6/7. (Jun. - Jul., 1982), pp. 179–189.
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Preston, Samuel, Patrick Heuveline, and Michel Guillot. 2000.Demography: Measuring and Modeling Population Processes. Blackwell Publishing.
Leonid A. Gavrilov & Natalia S. Gavrilova (1991),The Biology of Life Span: A Quantitative Approach. New York: Harwood Academic Publisher,ISBN3-7186-4983-7
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,ISBN978-3-642-15593-2
