31. Demography: definition, methods, data sources
- 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
- 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)
- 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
- Vital statistics registries