The Link Between the DTM & Population Structure (Age-Sex Structure / Pyramids) The composition of a population is known as population structure or age-sex structure. It can be represented by means of a population pyramid. The population is divided into groups depending on gender and on age. This is useful because it allows governments to plan ahead for the future needs of the population. It also allows comparisons to be made between the populations of different countries. Analysis of population structure can be related to other changes in the country, especially economic development (hence the link between population structure and the DTM). Population structure / Pyramids show: Life expectancy / longevity by their height Results of births minus deaths in specific age groups Results of past variations in birth rate (e.g. bulge due to the ‘baby boomers’ generation in the UK) Effects of migration (look for bulges and dips on the sides) Effects of events such as war, famine and disease (look for bulges and dips on the sides) In addition, population structure / pyramids allow the following to be calculated: The dependency ratio – the relationship between the working population and the dependent population In the EU young dependents are those aged 0-19 and old dependents are those aged pop 60+. This is obviously a crude generalisation of real life! If the combined number (%) of young and old dependents is divided by the ‘working population’ number (%) aged 20-59, then a figure for the dependency ratio is produced. Germany has a dependency ratio of 52 because for every 100 people in the working population, there are 52 people dependent on them. LICs often have even higher dependency ratios due to their large number of young dependents. A high ratio can cause problems – think why! Dependency ratio = Young dependents % + Old dependents % x 100 Working population % NB - It is not unusual for 0-14, 15-64 and 65+ to be used in data sets showing dependency ratios for different countries e.g. at www.indexmundi.com

The Link Between the DTM & Population Structure (Age-Sex Structure / Pyramids) The juvenility index shows the proportion of younger people in a population Juvenility index = % of the population under 20 x 100 % of the population over 20 A high index may be problematic but not always – think why/why not! The old-age index shows the proportion of elderly people in a population Old-age index = % of the population over 60 _ x 100 % of the population under 60 A high ratio is likely to be problematic 1. The DTM can be used to demonstrate changes in age-sex structure between countries and over time for the same country. For each stage of the DTM there is a characteristic shape of pyramid. Which stage do you think the following pyramids might be in? Why?

Stages 1-4 of the DTM and their Population Structures Note that each pyramid has lines drawn on it to separate the age cohorts 0-15, 16-65 and over 65. These are often considered to be young dependent, working age and retired sectors of the population respectively. Of course this is a marked oversimplification of reality. In HICs few people start work at 16 and many retire before 65. In LICs many children start work well before 16. 2. How would the population structure of a Stage 5 country be different to a Stage 4 country?

UK Population Pyramids 3. Which of the above pyramids is from the year 2000 and which is a projection for the year 2025? Explain how you arrived at your decision. 4. Identify (label) on both pyramids: the postwar baby boom, the 1960s baby boom, the low fertility of the late 1970s & early 1980s. 5. How would you expect a projection for the year 2050 to be different to the one for the year 2025? Explain your answer.

Other Population Pyramids 6. What observations and conclusions can you draw from each of the population pyramids below?