The adjusted infant mortality rate indicates the probability of dying before age one in a given cohort.

Age is time lived since birth. Demographers calculate age in a number of ways:
A. Age in completed years: age at last birthday, i.e. number of complete years lived by an individual at a given moment in time.
B. Age reached: difference between the current year and the year of birth. It is used to define a birth cohort.
C. Exact age: the exact period of time elapsed since birth and a measure that therefore increases continuously. It is expressed in years, months and days, or in tenths or hundredths of a year.

The age pyramid is a graphical representation of the age structure and sex structure of a population in a system of coordinates. While the x-axis represents the amount of men (usually on the left) and the amount of women (usually on the right), the y-axis represents the various age groups.

The age structure indicates the composition of a population by age groups, also known as age composition, or age distribution.

An ageing population is defined as a population in which the number of elderly (65+) is increasing relative to the number of 20-64 year olds.

The age-specific death rate is the number of deaths in a certain year in a certain age group, per capita of the population in that age group. Because there are important mortality differences between males and females, age-specific mortality rates are always calculated by sex. Differences in the age composition of populations are eliminated when using age-specific death rates.

The age-specific fertility rate denotes the number of live births per woman in a certain age group, per year. Differences in the age composition of populations are eliminated when using age-specific fertility rates.

Attrition is the process by which an original sample of a population is gradually reduced due to deaths, migration or non-response to a follow-up survey.

The average or mean can be calculated in a number of ways:
A. The arithmetic average / mean consists of the sum of a series of quantities divided by the number of quantities. When the term average or mean is used without further qualification, the arithmetic average is generally meant.
B. The geometric average/ mean is sometimes used when all observed values are positive. It is the Nth root of the product of N values.
C. A weighted average /mean is obtained when different items are given varying importance. It is calculated by multiplying each item by a particular weighting factor or weight.
D. The median is the value of the element that divides a set of observations into two halves.
E. The mode is the most common or frequent value in a set of observations.

Biases are systematic errors, e.g. introduced by the sampling strategy or interviewers when data are collected. Biases can cause observation errors in demographic research and affect estimates.

Population censuses are taken to obtain information about the state of the population at a given time. In a general census, all inhabitants of a particular country are counted simultaneously. In a partial census, only a section of the population is counted, e.g. the inhabitants of a given area. A micro census is limited to a sample of the population, usually large in size, and belongs in the category of sample surveys.

Cohabitation is the situation of people who share the same dwelling. As a simplification, the term cohabitants is often used to describe couples who live together without being married, and such unions are referred to as consensual unions.

A cohort is a group of persons who share a common characteristic or experience within a defined period of time. Thus a birth cohort is formed by a group of people who were born on a day or in a particular year or period. A marriage cohort is a group of persons married within a defined period. The primary objective of cohort analysis is the study of the intensity and tempo or timing of demographic phenomena in a specified cohort.

The crude birth rate is the number of live births per 1000 inhabitants in a certain year. It is quite easy to calculate and often used to measure the level of fertility. However, a major drawback is that the age structureof the population is not taken into account. For instance, the crude birth rate in an old population would be lower than in a young population.

The crude death rate indicates the number of deaths per 1000 inhabitants in a certain year. It is quite easy to calculate and frequently used to measure the level of mortality. However, a major drawback is that the age structure of the population is not taken into account. For instance, the crude death rate in an old population is higher than in a young population, which does not necessarily imply anything about the real mortality level.

Demographic pressure denotes the ratio between the number of youngsters plus elderly, on the one hand, and the number of 20-64 year olds, on the other hand. It is usually expressed as a percentage. Demographic pressure is a crude measure for the extent to which the "working" have to provide for the "non-working".

Demography studies developments in the size, composition, and spatial distribution of populations. The size and the structure of a population changes through births, deaths or spatial motion of its people.

The economically inactive population may be divided into dependents and self-supporting persons. Dependents rely on the efforts of earners for their support; for example, this is the case of housewives and dependent children. A special category of dependents is that of public welfare recipients or persons receiving public assistance.

The state of population decline.

The number of years required for a specified population to double in size at the current rate of population growth.

An earner is a member of the economically active population. An earner thus supports the social system or group and its dependents.

The ratio of the inactive to the active population is called the economic dependency ratio.

Emigration is moving away from the country of birth or citizenship.

An epidemic is a mass outbreak of a disease in a particular geographic area that spreads and then disappears relatively quickly.

An epidemiological transition or health transition is the period of mortality decline that accompanies the demographic transition. It is characterised by improved health, nutrition and organisation of health services and a change in the causes of death, with mortality from infectious diseases progressively being replaced by mortality from chronic and degenerative diseases and accidents.

Excess male mortality is an expression used to describe the excess mortality of men compared to the mortality of women. For a given age or age group it is usually measured as the ratio of the male mortality rate to the female mortality rate.

Fecundability is the probability of conceiving per menstrual cycle. A distinction is made between natural fecundability, in the absence of contraception, and residual fecundability in the opposite instance. The term effective fecundability designates fecundability in terms of conceptions that result in live births only. The conception rate during the period of exposure to risk is used to measure the effectiveness of contraception during periods of contraceptive use.

Fecundity is the biological capacity of a woman, a man or a couple to produce a live birth. Beyond individual variations, fecundity in women reaches its maximum at around age 20, starts decreasing slowly to age 35, and then more rapidly after age 35 until it falls to zero at around age 45 or 50.

Fertility and infertility refer to reproductive performance rather than capacity, and are used according to whether there was actual childbearing or not during the period under review. The fertility level can be assessed per woman, per couple, per group, or for a total population. In addition, fertility, like the number of births, can be distinguished by rank number (parity).

A fertility rate denotes the rate of births to a specified group, usually women, and is generally expressed as births per thousand. The denominator is usually the mid-year population in the stated period. The rates are calculated for groups of women and their women years. Male fertility rates are computed sometimes in an analogous manner. Fertility rates are generally expressed as births per thousand.
Other types of fertility rates are defined as follows:
A. Marital fertility ratesrelate the total number of marital births to the number of currently married women.
B. Non-marital fertility ratesrelate the total number of non-marital births to the number of single, widowed and divorced women.
C. General fertility ratesrelate the total number of births to all women of reproductive age (usually ages 15-44), regardless of marital status.
D. Completed fertility rates relate the average number of children actually born per woman in a cohort of women that has completed their childbearing years (usually age 44).
E. Total fertility rates (TFR) denote the sum of all age-specific fertility rates in a certain year. It gives the average number of children that a woman (or group of women) would have if each age-specific fertility rate would apply to her (or them) as observed in the period under consideration. The TFR is also known as the average number of children per woman.

Line of kinship uniting a child with its father and its mother.

Gender is a notion used in social sciences. It refers to the cultural dimension of sexual differentiation (such as the distribution of power or the breakdown of roles between men and women in society), while the notion of “sex” reflects a universal biological reality.

A household is a socio-economic unit of one or more persons who share housing and who jointly provide themselves with food and other necessities of life. An individual living alone is considered to be a one-person household. Definitions and classifications of households vary.

The Human Development Index (HDI) measures the average socio-economic development of a country by taking three factors into account: health, education and living standard of a population. The status of health is measured by looking at life expectancy at birth. The index for educational standard is calculated with the adult literacy rate and the combined primary to tertiary gross enrolment ratio. The basis for the index of living standard is the estimated earned income at purchasing power parity in US Dollars. The United Nations Development Programme (UNDP) has published the HDI since 1990 in its Human Development Reports.

Immigration is moving permanently or for a large time span to another country.

The number of new cases of a disease in a year in a given population.

Death of newborns before the age of 1.

The number of deaths (in a certain year) among children below age 1, per 1000 live births in that year.

The biological inability of a man, a woman or a couple to produce a live birth.

Intergenerational equity in economic, psychological, and sociological contexts is the concept or idea of fairness or justice in relationships between children, youth, adults and seniors, particularly in terms of treatment and interactions.

Intergenerational transfers are primarily economic transfers from one generation to the following. In all societies intergenerational transfers are prevalent and influence inequality and growth.

International migration is moving to another country. It can be separated into immigration and emigration. The difference between immigration and emigration is called the immigration balance or simply migration balance. To measure international migration three factors are taken into consideration: space, time and motivation.

Life expectancy is the average number of years a group of individuals can expect to live at a given age if mortality at each age remains constant in the future. The life expectancy at birth measure is a particular case that represents the mean length of life of individuals based on mortality at all ages. Life expectancy is calculated using life table methods and the reciprocal of life expectancy at birth is the life table death rate.

Source: Population Europe

A life table (also called a mortality table or actuarial table) is a table that shows, for each age, what the probability is that a person of that age will die before his or her next birthday. A number of inferences can be derived, such as the probability of surviving to any particular year of age and the remaining life expectancy for people at different ages.

Longitudinal or panel data are data from a (usually small) number of observations over time on a (usually large) number of cross-sectional units like individuals or households.

The mean age of a population is the average age of all its members.

The median age of a population is the age that divides the population into two numerically equal groups.

Migration is the process of moving to another area, usually implying movement across an administrative boundary. The administrative unit left by the migrant is the place of origin or place of departure; the unit to which the migrant moves is the place of destination or place of arrival. The concept of migration is often not applied to moves made by persons without a fixed place of residence, for example, nomads are excluded from the count of migrants in many countries. In general, geographic mobility does not include short-term trips that involve no change of usual residence, even though such moves may deserve study because of their economic and social importance.

Decisions about migration are shaped by economic, social, and cultural factors, so called push/pull factors. Migration models formalise these determinants. They also may describe the effects of migration at its origin and destination and the interactions between those effects. The simplest of these models are gravity models: the streams between the two areas are directly proportional to the size of their population, and inversely proportional to the distance between them.

Morbidity is the study of illness, sickness, ill-health or disease in a population. Two aspects are considered: the incidence of disease and the prevalence of disease according to whether the new cases of disease are considered or the number of cases existing at one point in time. The compilation of morbidity statistics is hampered by the lack of a sharp distinction between health and the morbid state. Nosology and nosography contribute respectively to the classification and description of diseases.

The demographic concept of mortality deals with the effect of death on the population. Mortality is an important component of population growth. All people die, but the age at which that will happen has strong demographic consequences.

A mortality crisis is a sudden, large increase in the death rate.

The general terms mortality rate and death rate encompass all the rates that measure the frequency of deaths.

Natality generally refers to birth rates and is a component of population change. Natality depends on the number of women in a population and their fertility.

The natural increase of a population is the excess of births over deaths.

The net migration encompasses the number of people moving in minus the number of people moving out of a population. It contributes to overall population growth and can have a negative or a positive sign. Net immigration, or net in-migration, is used when arrivals exceed departures, and net emigration, or net out-migration, when the opposite is true. The sum of arrivals and departures in a country can be used to measure the volume of migration. A similar concept, applied to sub-areas of a country, is the migration turnover.

The average number of daughters that a new-born girl would have during her lifetime if the age-specific fertility rates and mortality rates as observed in a certain year were to remain applicable.

Non-renewable events are events such as fatal diseases, deaths, etc. Together with renewable events they comprise the statistics of population change.

The systematic description of diseases.

The study of disease.

The study of nuptiality deals with the frequency and timing of marriages, with the characteristics of persons united in marriage, and with the dissolution of such unions.

The abbreviation NUTS (French: Nomenclature des Unités Territoriales Statistiques) refers to a system that aims to precisely identify the regions of the European Union. In order to be able to compare spaces and statistics, regions are hierarchically organised based on existing administrative entities and similar sizes of populations: NUTS-level 0 - nation states; NUTS-level 1 - larger regions/ parts of a state; NUTS-level 2 - medium sized regions/landscapes of a state; NUTS-level 3 - smaller regions/large cities of a state. The NUTS-classification is used, for example, in regional socio-economic analyses as well as in the allocation of EU structural funds.

The odds in favour of an event or a proposition are expressed as the ratio of a pair of integers, which is the ratio of the probability that an event will happen to the probability that it will not happen.

An epidemic that spreads over a very wide area.

The number of children previously born alive to a woman. Two-parity women have had two children and zero parity women have had no live births.

The place where a person lives is called the place of residence.

A marriage in which a person of one sex has more than one spouse of the opposite sex. Polyandry occurs when a woman has more than one husband, and polygamy when a man has several wives. Polygamy contrasts with monogamy. When a person has two spouses the term bigamy is used.

The actual or de facto population is made up of the people in a specific area on census day, including visitors or transients. This marks a distinction to the resident or de jure population of the area, which only considers those that habitually live in the area. Here, temporary absentees are also included.

Population decline is negative population growth.

A population forecast is a projection in which a set of assumptions are considered to yield a realistic picture of the probable future development of a population. Although the projection period is variable, short-term forecasts are the rule, as the margin of error to which forecasts are subject increases considerably as the length of the forecast’s period increases. The most frequently used method of projection is the component method or cohort-component method, which takes the population distributed by age and sex at a base date and carries it forward in time, cohort by cohort, on the basis of separate allowances for fertility, mortality and migration.

The extent to which a population increases or decreases over a certain period. It always refers to a certain area and to a certain period (usually one year). Population growth can be measured in numbers of inhabitants, but is usually expressed as a percentage, the so-called growth rate.

Population projections are calculations that show the future development of a population when certain assumptions are made about the future course of population change, usually with respect to fertility, mortality and migration. They are in general purely formal calculations, developing the implications of the assumptions that are made.

A population register denotes a system of continuous registration in a country. In these registers, every member of the population or every family may be represented, and the register is maintained or updated through information that reaches it through the local registration offices and through registration of any changes of residence. It is usually matched with census results and brought up to date at regular intervals by special checks.

The population structure is the composition of a population according to certain characteristics. In demography, age and sex are the most frequently used characteristics; marital status and region are also important. Other characteristics include nationality, country of birth, religious affiliation, and educational level.

Predicted or expected probabilities can be calculated empirically or from functions that predict or model the probability of an outcome or range of outcomes. This means that if a study is conducted with 100 subjects the outcome can be projected onto the rest of the population.

The number of sick people at a given time.

The propensity of an event is its natural inclination or tendency.

Push and pull factors divide migration models into two broad categories based on migration streams between two areas. Social, economic or demographic variables play decisive roles. These variables are classified as push factors when they characterize repulsion from the area of origin, as pull factors resulting in attraction to the area of destination, and as intervening obstacles between the two areas.

The aim of qualitative analysis is in-depth understanding of human behaviour and the reasons that govern that behaviour. It allows for more exploratory research and fine distinctions to be drawn in information gathered because it does not require the data to fit into a finite number of classifications. This type of research relies on small, focused samples rather than the larger representative samples of quantitative research. Quantitative researchers seek to understand human behavior by assigning a numerical value to variables that aim to capture reality and using mathematical and statistical modeling to assess relationships between these variables. Findings can be generalised to a larger population in quantitative research as long as valid sampling techniques have been used.

Recognition is the act of declaring oneself to be the father or mother of a child born outside marriage. When a child is recognised before or at the time of birth, this recognition is indicated on the birth certificate.

A reconstituted family is composed of an adult couple, married or unmarried, living with at least one child born from a previous union of one of the partners.

In statistics, regression analysis includes techniques for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables. More specifically, regression analysis helps one understand how the typical value of the dependent variable changes when any one of the independent variables is varied, while the other independent variables are held fixed. Most commonly, regression analysis estimates the conditional expectation of the dependent variable given the independent variables — that is, the average value of the dependent variable when the independent variables are held fixed.

An increase in the proportion of young people involves a rejuvenation of the population.

Renewable events are events such as pregnancies, births or migratory moves. They are assigned in an order based on the number of previous events of the same nature for the same person. Together with non-renewable events they comprise the statistics of population change.

A rentier is a person that lives off regular payments of invested capital or off the lease of land.

The study of reproduction or population replacement is concerned with the natural process through which a population replaces its numbers. A distinction is drawn between gross reproduction or gross replacement, where no account is taken of mortality before the end of the reproductive period, and net reproduction or net replacement, in which mortality is taken into account.

Reproduction rates are generally female reproduction rates or maternal reproduction rates. The female net reproduction rate is defined as the average number of live daughters that would be born to a hypothetical female birth cohort, which would be subjected to a set of current age-specific fertility rates and mortality rates.

The reproductive period begins at puberty. Menstruation — the appearance of the periods or menses in women — also begins at puberty. The first period is called the menarche and menstruation ceases with menopause, which is also sometimes called the climacteric. In practice, the reproductive period is often made to start, by convention, at 15 years or at the minimum age at marriage and, for some, to end at 45 or 50 year. The temporary absence of menstruation, be it normal or pathological, is called amenorrhea. Pregnancy amenorrhea occurs after a conception, and post-partum amenorrhea after a birth.

A sample whose elements are selected by a chance process is referred to as a random sample or probability sample. If a complete list of sampling units is available, this is called a sampling frame. In simple random sampling a proportion of sampling units is selected from the frame at random. This proportion is called the sampling fraction or sampling ratio. Systematic samples are drawn systematically from a frame in which the sampling units are consecutively numbered. In cluster sampling, population elements are not drawn individually, but in groups that are called clusters.

The term selection bias or selection effect most often refers to the distortion of a statistical analysis resulting from the method of collecting samples, i.e. when an error in choosing the individuals or groups to take part in a scientific study exists. If the selection bias is not taken into account, any conclusions drawn from the study may be wrong.

Self-supporting persons have sufficient means for their subsistence. They may be earners, rentieror persons of independent means, retired persons or pensioners.

The sex ratio is the ratio of the number of males to the number of females. It is usually expressed as an index value, i.e. the number of males per 100 females.

Simulation is one form of demographic modelling in which specific values of the variables are included in a system of relations. In other words, a simulation represents the evolution of a population (of individuals, couples, families, households, etc.) and its structure on the basis of its initial state and the effect of various demographic variables (such as fertility, fecundability, mortality, etc.). A distinction is made between deterministic models, which assign functional relations between definite values of the variables, as if the studied population were infinitely large, and stochastic models or probabilistic models, which consider the probability of various events occurring to individuals over the duration of the process under study.

The standardised death rate denotes the number of people per 1000 inhabitants that would have died in a certain year if the age structure of the population would have had a certain distribution. Standardisation is a method to eliminate the effect of the age structure on the death rate and make death rates of different populations comparable.

A birth occurring after 24 weeks of gestation in which the foetus is dead. The expulsion or extraction of an embryo or foetus before the 6^th month of pregnancy is called an abortion or a miscarriage.

The target year is the year in which a forecast variable reaches its ultimate value for the first time.

Persons incapable of work are called unemployable.

Women years are the number of years lived by a given number of women in an interval.