The basic demographic tools
Knowing the size of a population is a simple matter of counting the individuals who make up that population at a given time. This is done through a census or population survey. During this counting of the population, key characteristics such as age and sex are recorded. This allows us to build a picture of the structure of the population, as well as the size. Although age and sex are the most basic details we would wish to record, other information is often recorded alongside, such as occupation, religion, ethnicity, marital status and so on. Once we have this information, we can describe the population and compare it with others through the use of proportions and ratios.
We can also combine information on the population stock (size and structure) with information on the numbers of demographic events, or population-flows to calculate rates. These rates can then be compared with the rates of other populations, or other sub-groups of the same population, and can be used when considering the population dynamics and making population projections.
The first part of this session will look at how demographers describe the age and sex structure of a population. The second part will introduce you to some of the basic calculations used by demographers when describing population structure and demographic events. Lastly, the difference between period and cohort data will be described.