Demography is the scientific study of the determinants and consequences of changes in human population
You can only enter a population by birth or migration, and you can only leave it by death or migration
Therefore, fertility, mortality, and migration are important in the study of demographics
Keeping record of birth and death is simple; migration is not always registered and therefore more difficult to keep record of
Variables in demography
Age
Gender
Income
Occupation
Health service use
Geographic location
Geographic density
T.R. Malthus – first person to draw attention to fertility and mortality
He postulated that population tends to grow geometrically while food supply grew only arithmetically (i.e., the population grows much faster than the food supply)
This is sometimes called the Malthusian trap
Because of the Malthusian trap, war, disease, hunger would control the population growth
However, the industrial revolution made an exponential growth in food supply possible, bypassing the Malthusian trap and allowing for a population explosion
Data sources
Vital statistics registries
Vital statistics registries continuously collect information of demographic events like birth, deaths, marriages, etc., as they occur
Census
A census occurs every 10 years and collects demographic and other data at that point in time
While vital statistics registries are continuously collected, a census occurs only every 10 years
The collection of this data can occur by sending out questionnaires in the mail, or by collecting data from digital registers
Direct data can be collected from registries of vital statistics or censuses
These registries track all births, deaths, marriage, divorce, migration
In developed countries these are the best sources
Indirect data can be collected by asking women how many sisters have died or had children, asking people about siblings, parents, etc.
From this, researchers can indirectly estimate data for the whole population
Necessary in countries which don’t keep registries
