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78-454: The NHANES interview includes demographic , socioeconomic , dietary , and health-related questions. The examination component consists of medical, dental , and physiological measurements, as well as laboratory tests administered by medical personnel. The National Health Survey Act was passed in 1956. This allowed legislative authorization to provide current statistical data on the amount, distribution, and effects on illness and disability in

156-475: A leap year has 29 days instead of the usual 28, so the year lasts 366 days instead of the usual 365. A person born on February 29 may be called a " leapling " or a "leaper". In common years, they usually celebrate their birthdays on February 28. In some situations, March 1 is used as the birthday in a non-leap year since it is the day following February 28. Technically, a leapling will have fewer birthday anniversaries than their age in years. This phenomenon

234-494: A pagan custom. Saint's days were typically celebrated on the anniversary of their martyrdom or death, considered the occasion of or preparation for their entrance into Heaven or the New Jerusalem . Ordinary folk celebrated their saint's day (the saint they were named after), but nobility celebrated the anniversary of their birth. The "Squire's Tale", one of Chaucer's Canterbury Tales , opens as King Cambuskan proclaims

312-468: A significant comparison, numbers must be altered for the size of the population that is under study. For example, the fertility 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. Within

390-422: A ' name day ', otherwise known as a 'Saint's day'. It is celebrated in much the same way as a birthday, but it is held on the official day of a saint with the same Christian name as the birthday person; the difference being that one may look up a person's name day in a calendar, or easily remember common name days (for example, John or Mary ); however in pious traditions, the two were often made to concur by giving

468-708: A 16.9% decrease in Caesarean births on Halloween , compared to dates occurring within one week before and one week after the October holiday. In contrast, on Valentine's Day there is a 3.6% increase in spontaneous births and a 12.1% increase in Caesarean births. In Sweden 9.3% of the population is born in March and 7.3% in November when a uniform distribution would give 8.3%. In the Gregorian calendar (a common solar calendar ), February in

546-401: A country (or other entity) contains Population t persons at time t . What is the size of the population at time t + 1 ? Natural increase from time t to t + 1: Net migration from time t to t + 1: 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

624-503: A feast to celebrate his birthday. The Catholic Church , the Eastern Orthodox Church and Protestantism , i.e. the three main branches of Christianity , as well as almost all Christian religious denominations, consider celebrating birthdays acceptable or at most a choice of the individual. An exception are Jehovah's Witnesses , who do not celebrate them for various reasons: in their interpretation this feast has pagan origins,

702-484: A field of sociology , though there are a number of independent demography departments. 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 of social actors can change across time through processes of birth, death, and migration . In the context of human biological populations, demographic analysis uses administrative records to develop an independent estimate of

780-539: A fixed day of the year, which may not necessarily match the day of their birth, but on which celebrations are held. Examples are: Birthdays are fairly evenly distributed through the year, with some seasonal effects. In the United States, there tend to be more births in September and October. This may be because there is a holiday season nine months before (the human gestation period is about nine months), or because

858-400: A highly formal, ritualized manner. They treat Buddha's statue as if it was Buddha himself, as if he were alive; bathing, and "feeding" him. Hindus celebrate the birth anniversary day every year when the day that corresponds to the lunar month or solar month (Sun Signs Nirayana System – Sourava Mana Masa) of birth and has the same asterism (Star/Nakshatra) as that of the date of birth. That age

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936-460: 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 bank loan 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

1014-436: A newborn the name of a saint celebrated on its day of confirmation , more seldom one's birthday. Some are given the name of the religious feast of their christening's day or birthday, for example, Noel or Pascal (French for Christmas and "of Easter"); as another example, Togliatti was given Palmiro as his first name because he was born on Palm Sunday . Some notables, particularly monarchs, have an official birthday on

1092-498: 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 Quetelet (1796–1874), William Farr (1807–1883), Louis-Adolphe Bertillon (1821–1883) and his son Jacques (1851–1922), Joseph Körösi (1844–1906), Anders Nicolas Kaier (1838–1919), Richard Böckh (1824–1907), Émile Durkheim (1858–1917), Wilhelm Lexis (1837–1914), and Luigi Bodio (1840–1920) contributed to

1170-418: A silent wish and attempt to blow out the candles in one breath; if successful, superstition holds that the wish will be granted. In many cultures, the wish must be kept secret or it will not "come true". Presents are bestowed on the individual by the guests appropriate to their age. Other birthday activities may include entertainment (sometimes by a hired professional, i.e. a clown, magician, or musician), and

1248-406: A special toast or speech by the birthday celebrant. The last stanza of Patty Hill 's and Mildred Hill 's famous song, "Good Morning to You" (unofficially titled " Happy Birthday to You ") is typically sung by the guests at some point in the proceedings. In some countries, a piñata takes the place of a cake. In some historically Roman Catholic and Eastern Orthodox countries, it is common to have

1326-426: A standardized mortality rate (SMR) or standardized incidence rate (SIR). 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 earlier census . The best way of measuring population change

1404-544: A theme for some gifts or decorations. Because of the importance attached to the influence of these stars in ancient China and throughout the Sinosphere , East Asian age reckoning previously began with one at birth and then added years at each Chinese New Year, so that it formed a record of the suì one had lived through rather than of the exact amount of time from one's birth. This method—which can differ by as much as two years of age from other systems—is increasingly uncommon and

1482-489: A thirteen-day period, between September 22 and October 4. The ten least common birthdays (other than February 29) are December 24–27, January 1–2, February 6 , March 22, April 1 and April 25 . This is based on all live births registered in New Zealand between 1980 and 2017. Positive and negative associations with culturally significant dates may influence birth rates. The study shows a 5.3% decrease in spontaneous births and

1560-499: A variety of demographic methods for modelling population processes. They include models of mortality (including the life table , Gompertz models , hazards models , Cox proportional hazards models , multiple decrement life tables , Brass relational logits), fertility (Hermes model, Coale -Trussell models, parity progression ratios ), marriage (Singulate Mean at Marriage, Page model), disability ( Sullivan's method , multistate life tables), population projections ( Lee-Carter model ,

1638-601: Is a distinction between birth day and birth date (also known as date of birth): the former, except for February 29 , occurs each year (e.g. January 15), while the latter is the complete date when a person was born (e.g. January 15, 2001). In most legal systems, one becomes a legal adult on a particular birthday when they reach the age of majority (usually between 12 and 21), and reaching age-specific milestones confers particular rights and responsibilities. At certain ages, one may become eligible to leave full-time education , become subject to military conscription or to enlist in

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1716-437: 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. Date of birth A birthday

1794-417: 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 , which summarizes mortality separately at each age. A life table is necessary to give a good estimate of life expectancy. Suppose that

1872-501: Is entirely different from the usual word for "year(s)" ( 年 , nián ), reflecting the former importance of Chinese astrology and the belief that one's fate was bound to the stars imagined to be in opposition to the planet Jupiter at the time of one's birth. The importance of this duodecennial orbital cycle only survives in popular culture as the 12 animals of the Chinese zodiac , which change each Chinese New Year and may be used as

1950-721: Is exploited when a person claims to be only a quarter of their actual age, by counting their leap-year birthday anniversaries only. In Gilbert and Sullivan 's 1879 comic opera The Pirates of Penzance , Frederic the pirate apprentice discovers that he is bound to serve the pirates until his 21st birthday rather than until his 21st year. For legal purposes, legal birthdays depend on how local laws count time intervals. Some studies show people are more likely to die on their birthdays, with explanations including excessive drinking, suicide, cardiovascular events due to high stress or happiness, efforts to postpone death for major social events, and death certificate paperwork errors. In Judaism ,

2028-629: Is known as Gurpurb . According to Herodotus (5th century BC), of all the days in the year, the one which the Persians celebrate most is their birthday. It was customary to have the board furnished on that day with an ampler supply than common: the richer people eat wholly baked cow, horse, camel, or donkey (Greek: ὄνον ), while the poorer classes use instead the smaller kinds of cattle. The Romans enthusiastically celebrated birthdays with hedonistic parties and generous presents. The Chinese word for "year(s) old" ( t 歲 , s 岁 , suì )

2106-431: 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 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

2184-521: Is not used for official purposes in the PRC or on Taiwan , although the word suì is still used for describing age. Traditionally, Chinese birthdays—when celebrated—were reckoned using the lunisolar calendar , which varies from the Gregorian calendar by as much as a month forward or backward depending on the year. Celebrating the lunisolar birthday remains common on Taiwan while growing increasingly uncommon on

2262-405: Is reckoned whenever Janma Nakshatra of the same month passes. Hindus regard death to be more auspicious than birth, since the person is liberated from the bondages of material society. Also, traditionally, rituals & prayers for the departed are observed on 5th and 11th day with many relatives gathering. Sikhs celebrate the anniversary of the birth of Guru Nanak and other Sikh Gurus which

2340-545: Is seen as the intellectual father of ideas of overpopulation and the limits to growth. Later, more sophisticated and realistic models were presented by Benjamin Gompertz 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

2418-428: Is the anniversary of the birth of a person, or figuratively of an institution . Birthdays of people are celebrated in numerous cultures, often with birthday gifts , birthday cards , a birthday party , or a rite of passage . Many religions celebrate the birth of their founders or religious figures with special holidays (e.g. Christmas , Mawlid , Buddha's Birthday , Krishna Janmashtami , and Gurpurb ). There

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2496-473: Is the statistical study of human populations : their size, composition (e.g., ethnic group, age), and how they change through the interplay of fertility (births), mortality (deaths), and migration. Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as education , nationality , religion , and ethnicity . Educational institutions usually treat demography as

2574-554: Is the case in much of the developing world, and most of historical 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. There are

2652-432: 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 , economics , epidemiology , geography , anthropology and history , demography offers tools to approach a large range of population issues by combining a more technical quantitative approach that represents

2730-510: 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. Demographic analysis is usually abbreviated as DA. For the 2010 U.S. Census, The U.S. Census Bureau has expanded its DA categories. 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. Patient demographics form

2808-421: 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 a percentage . When this statistic is achieved, the population growth between two or more nations that differ in size, can be accurately measured and examined. For there to be

2886-708: The American occupation that followed World War II . Children's birthday parties are the most important, typically celebrated with a cake, candles, and singing. Adults often just celebrate with their partner. In North Korea , the Day of the Sun , Kim Il Sung 's birthday, is the most important public holiday of the country, and Kim Jong Il 's birthday is celebrated as the Day of the Shining Star . North Koreans are not permitted to celebrate birthdays on July 8 and December 17 because these were

2964-707: 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 . Population composition is the description of population defined by characteristics such as age, race , sex or marital status . These descriptions can be necessary for understanding

3042-649: The Leslie Matrix ), and population momentum ( 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 Study , the 1970 British Cohort Study , 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

3120-505: The Middle Ages , Christian thinkers devoted much time in refuting the Classical ideas on demography. Important contributors to the field were William of Conches , Bartholomew of Lucca , William of Auvergne , William of Pagula , and Muslim sociologists like Ibn Khaldun . One of the earliest demographic studies in the modern period was Natural and Political Observations Made upon

3198-469: The United States and Europe celebrate birthdays as customary especially for children, while some abstain. There is also much controversy regarding the permissibility of celebrating Mawlid , (the anniversary of the birth of Muhammad ), as some Muslims judge the custom as an unacceptable practice according to Islamic tradition. Many monasteries celebrate the anniversary of Buddha's birth, usually in

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3276-510: The United States and much of Europe ), registry statistics are the best method for estimating the number of births and deaths. A 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

3354-666: The life table , 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

3432-590: The rabbis are divided about celebrating this custom, although it is accepted by the majority of the faithful. In the Torah the only mention that is made of the birthday, refers to the celebration of Pharaoh's birthday in Egypt, as recorded in Genesis (Parashat Vaieshev) 40:20. Origen in his commentary "On Levites" wrote that Christians should not only refrain from celebrating their birthdays, but should look on them with disgust as

3510-515: The red 100 RMB notes —are the usual gift from relatives and close family friends for most children. Gifts for adults on their birthday are much less common, although the birthday for each decade is a larger occasion that might prompt a large dinner and celebration. The Japanese reckoned their birthdays by the Chinese system until the Meiji Reforms . Celebrations remained uncommon or muted until after

3588-433: The social dynamics from historical and comparative research. This data is often compared using a population 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 as population size ). Lack of information on

3666-730: The Application of Probabilities to Life Contingencies (1838). In 1755, Benjamin Franklin published his essay Observations Concerning the Increase of Mankind, Peopling of Countries, etc. , projecting exponential growth in British colonies . His work influenced 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 ). Malthus

3744-556: The Bills of Mortality (1662) by John Graunt , which contains a primitive form of life table . Among the study's findings were that one-third of the children in London died before their sixteenth birthday. Mathematicians, such as Edmond 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, followed later by Augustus De Morgan , On

3822-488: The US. In the United States between 1973 and 1999, September 16 is the most common birthday in the United States and December 25 the least common birthday (other than February 29, because of leap years). In 2011, October 5 and 6 were reported as the most frequently occurring birthdays. In New Zealand, the most common birthday is September 29, and the least common birthday is December 25. The ten most common birthdays all fall within

3900-494: The United States. The first three national health examination surveys were conducted in the 1960s: The first NHANES was conducted in 1971, and in 1999 the surveys became an annual event; the first report on the topic was published in 2001. NHANES findings are used to determine the prevalence of major diseases and risk factors for diseases. Information is used to assess nutritional status and its association with health promotion and disease prevention . NHANES findings are also

3978-467: 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 of world population out to

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4056-713: The basis for national standards for such measurements as height , weight , and blood pressure . NHANES data are used in epidemiological studies and health sciences research (including biomarkers of aging ), which help develop sound public health policy , direct and design health programs and services, expand health knowledge, extend healthspan and lifespan . Follow-up studies using NHANES data were made possible by creating linked mortality files and files based on Medicare and Medicaid data. Demographics Demography (from Ancient Greek δῆμος ( dêmos )  'people, society' and -γραφία ( -graphía )  'writing, drawing, description')

4134-696: 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 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

4212-518: The category of standardization , there are two major approaches: direct standardization and indirect standardization. A stable population does not necessarily remain fixed in size. It can be expanding or shrinking. 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

4290-553: 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 of death , postal code, ethnicity, blood type , emergency contact information, family doctor, insurance provider data, allergies , major diagnoses and major medical history. Formal demography limits its object of study to

4368-494: 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 (International Committee for Coordination of Demographic Research) network while most individual scientists engaged in demographic research are members of

4446-531: The dates of the deaths of Kim Il Sung and Kim Jong Il , respectively. More than 100,000 North Koreans celebrate displaced birthdays on July 9 and December 18 instead to avoid these dates. A person born on July 8 before 1994 may change their birthday, with official recognition. South Korea was one of the last countries to use a form of East Asian age reckoning for many official purposes. Prior to June 2023, three systems were used together—"Korean ages" that start with 1 at birth and increase every January 1st with

4524-528: The development of demography and to the toolkit of methods and techniques of demographic analysis. Demography is the statistical and mathematical study of the size, composition, and spatial 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 like birth , deaths , migrations, marriages, divorces , diseases, and employment . To do this, there needs to be an understanding of how they are calculated and

4602-644: The distribution and abundance of organisms. As it relates to organizations and demography, organizations go through various liabilities 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 by environmental factors . Among several factors of

4680-408: 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

4758-508: The legal control and legal responsibilities of their parents or guardians over and for them. Most countries set the age of majority at 18, though it varies by jurisdiction. Many cultures have one or more coming of age birthdays: The birthdays of historically significant people, such as national heroes or founders, are often commemorated by an official holiday marking the anniversary of their birth. An individual's Beddian birthday, named in tribute to firefighter Bobby Beddia, occurs during

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4836-519: The longest nights of the year also occur in the Northern Hemisphere nine months before. However, it appears the holidays have more of an effect on birth rates than the winter: New Zealand , a Southern Hemisphere country, has the same September and October peak with no corresponding peak in March and April. The least common birthdays tend to fall around public holidays, such as Christmas , New Year's Day and fixed-date holidays such as July 4 in

4914-575: The mainland. Birthday traditions reflected the culture's deep-seated focus on longevity and wordplay. From the homophony in some dialects between 酒 (" rice wine ") and 久 (meaning "long" in the sense of time passing), osmanthus and other rice wines are traditional gifts for birthdays in China . Longevity noodles are another traditional food consumed on the day, although western-style birthday cakes are increasingly common among urban Chinese. Hongbaos —red envelopes stuffed with money, now especially

4992-418: The measurement of population processes, while the broader field of social demography or population studies also analyses the relationships between economic, social, institutional, cultural, and biological processes influencing a population. Demographic thoughts traced back to antiquity, and were present in many civilisations and cultures, like Ancient Greece , Ancient Rome , China and India . Made up of

5070-459: The military, to consent to sexual intercourse , to marry with parental consent , to marry without parental consent, to vote , to run for elected office, to legally purchase (or consume) alcohol and tobacco products, to purchase lottery tickets, or to obtain a driver's licence . The age of majority is the age when minors cease to legally be considered children and assume control over their persons, actions, and decisions, thereby terminating

5148-413: 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. People decide to exit organizations for many reasons, such as, better jobs, dissatisfaction, and concerns within

5226-458: The original data-collection procedures may prevent accurate evaluation of data quality. The demographic analysis of labor markets can be used to show slow population growth, population aging , 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. The population is expected to grow more slowly and age more rapidly than ever before and

5304-528: The population. Demographic analysis estimates are often considered a reliable standard for judging the accuracy of the census information gathered at any time. In the labor force , demographic analysis is used to estimate sizes and flows of populations of workers; in population 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 and institutional forms. Demographic analysis

5382-512: 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 , Thucydides , Hippocrates , Epicurus , Protagoras , Polus , Plato and Aristotle . In Rome, writers and philosophers like Cicero , Seneca , Pliny the Elder , Marcus Aurelius , Epictetus , Cato , and Columella also expressed important ideas on this ground. In

5460-566: The questions they answer which are included in these four concepts: population change , standardization of population numbers, the demographic bookkeeping equation, and population composition. There are two types of data 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

5538-417: 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

5616-447: 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. 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

5694-404: 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. 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

5772-474: 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 gather information on births and deaths that occurred in the 18 months immediately preceding the census. Indirect methods of collecting data are required in countries and periods where full data are not available, such as

5850-518: 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 in Austria expect world population to peak at 9 billion by 2070. Throughout the 21st century, the average age of the population

5928-525: The year following their birth on January 1 in the Northern Hemisphere and August 1 in the Southern Hemisphere. In certain parts of the world, an individual's birthday is celebrated by a party featuring a specially made cake . It may be decorated with lettering and the person's age, or studded with the same number of lit candles as the age of the individual. The celebrated individual may make

6006-399: The year that their age matches the last two digits of the year they were born. In many cultures and jurisdictions, if a person's real birthday is not known (for example, if they are an orphan), then their birthday may be adopted or assigned to a specific day of the year, such as January 1. The birthday of Jesus is celebrated at Christmas . Racehorses are reckoned to become one year old in

6084-499: Was not celebrated by early Christians, is negatively expounded in the Holy Scriptures and has customs linked to superstition and magic . The birthday does not reflect Islamic tradition, and because of this, the majority of Muslims refrain from celebrating it. Others do not object, as long as it is not accompanied by behavior contrary to Islamic tradition. A good portion of Muslims (and Arab Christians ) who have emigrated to

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