Topics: Human Geography - Demography
The word dates from 1880, from French demographie (from Greek demos, people + French –graphie, -graphy. It is 'the statistical study of human populations especially with reference to size and density, distribution, and vital statistics'. (Merrian-Webster Dictionary)
'Changes in population provide the background to which the development of society has to adjust. Population changes relate to all the phenomena concerning people: births, deaths, migration, marriages and divorces. These phenomena not only touch individuals in society but also impinge on the structure of society more widely. Demography studies population development, that is, the number of births, deaths and migration and other phenomena influencing population change, such as the marriage and divorce rates of the population. Demography also examines what kinds of effects changes in population have on the economic and social development of society.' (Statistics Finland)
Among the terms and concept used in demography are:
Crude birth rate (b): for a population during a given year, is defined as the total number of births (B) divided by the midyear population (P), expressed per thousand population: b = 1000 * (B/P)
Age-specific fertility rate (asfr): asfr for women of age group i in a population during a given year is the total number of births to women age i during the year (Bi) divided by the total (midyear) number of women age i (Wi). Expressed per thousand: asfri = 1000 * (Bi/Wi)
Total fertility rate (TFR): is the sum of age-specific fertility rates from the minimum to the maximum age at which childbearing occurs, multiplied by the number of years in each age group and divided by 1000. If age groups are for five-year intervals (15-19, 20-24, etc.), TFR = ("SUM" asfri * 5)/1000
Replacement fertility: is the level of fertility at which a population just replaces itself. In a world with no mortality, replacement fertility would exist with a TFR of 2.0.
Crude death rate (cdr): for a population in a given year, is the total number of deaths (D) divided by the midyear population (P) expressed per thousand population: d = 1000 * (D/P)
Age-specific death rate (asdr): for individuals age i in a population during a given year is defined as the total number of deaths to people age i during the year (Di) divided by the total (midyear) population age i (Pi). Expressed per thousand: asdri = 1000 * (Di/Pi) .
Life expectancy at birth: indicates the average number of years that a newborn baby can expect to live.
Source: Penn State University