Presentation on theme: "Population Pyramids IB SL. Population Pyramids – The Basics Population pyramids show a cross section of a population at a particular moment. They divide."— Presentation transcript:
Population Pyramids IB SL
Population Pyramids – The Basics Population pyramids show a cross section of a population at a particular moment. They divide the population by gender i.e. male and female and by age. The age groups are called cohorts. Gender – male and female Age groups or cohorts – usually in 5 year age groups e.g
What Info Can We Get From A Population Pyramid? If one cohort is smaller than the one below it, this could be explained by: – A decline in birth rate – An increase in death rate – Migration – Any combination of these As you can see from the population pyramid, the cohort for 20 – 24 year olds is smaller than the cohort for 15 – 19 year olds. Therefore this means that 20 – 25 years ago there was a decline in the birth rate, or that this cohort has been affected by an increased death rate, or that large numbers in this cohort have migrated (or a combination of any of these.)
Can Population Pyramids Explain What Happened? The simple answer is no, a population pyramid is a descriptive tool. It can only describe what is happening now and in the past in terms of the age and sex of the population. It doesnt predict patterns in the future. It cant explain patterns now or in the past. It doesnt include other features of populations e.g. religion, ethnic group etc.
Use Your Common Sense! You can make educated guesses about what happened, but be aware that they are just guesses! Why is the female bar wider for 80+ year olds? It might be because females generally have a greater life expectancy than males so tend to live longer Why is there a bulge in the 35 – 49 cohort for both males and females? It might be because the older ones in this cohort (45 – 49) were born just after World War II when all of the men returned from war and so there was a Baby Boom i.e. more babies were born. The younger ones in this cohort were born in the 1960s and so the increase might be due to more free attitudes towards sex. Why is there an indent in the 20 – 29 cohort? This may be due to a decreased Birth Rate in the 1980s due to more women having careers and so leaving having children until they are in their late 20s and 30s. This means that their fertility window is reduced.
Features of LEDC Pyramids LEDC population pyramids have fairly broad bases – this suggests a high Birth Rate LEDC population pyramids have very narrow tops – this suggests a high Death Rate and a low life expectancy LEDC population pyramids have steeply sloping sides as many people in each successive cohort die – this suggests a high Death Rate LEDC population pyramids have many more people in the youthful pyramid base i.e. it looks more pyramid in shape compared to the MEDC pyramid
Features of MEDC Pyramids MEDC population pyramids have fairly narrow bottoms – which means a fairly low Birth Rate MEDC population pyramids have fairly wide tops – which suggests that there is a low Death Rate and high life expectancy. Large numbers of people are living until 80+. MEDC population pyramids have gently sloping sides – this suggests that there is a low Death Rate. MEDC population pyramids tend to have more people in the top half of the pyramid and lower numbers of younger people – this gives a rather top heavy appearance.
Population pyramids are used to show information about the age and gender of people in a specific country. MaleFemale Population in millions In this country there is a high Birth Rate There is also a high Death Rate. This population pyramid is typical of countries in poorer parts of the world (LEDCs.)
In some LEDCs the government is encouraging couples to have smaller families. This means the birth rate has fallen.
MaleFemale Population in millions In this country the number of people in each age group is about the same. The largest category of people were born about 40 years ago. In this country there is a low Birth Rate and a low Death Rate. This population pyramid is typical of countries in the richer parts of the world (MEDCs.)
Population in millions MaleFemale In this country the birth rate is decreasing. In the future the elderly people will make up the largest section of the population in this country. This is happening more and more in many of the worlds richer countries.
Male Female Population in thousands This country has a large number of temporary workers. These are people who migrate here especially to find a job.
Population pyramid for Mozambique. Population pyramid for Iceland.
What happens next?
What is going to happen to Japans population in the future? Why does this matter?
MEDCs and LEDCs Look at your 2 Population Pyramids and add the following labels to each pyramid (some can be used more than once).
Which Labels Go Where? Primary school class sizes fall High birth rate Low death rate Low birth rate High death rate New maternity hospital is needed New shopmobility needed More Golden Weddings Public health inspector happy at creation of new sewer. Parents start to think more about family planning Grandparents are rare Rise in taxes to pay for growing dependants Hospital in UK advertises in India for new staff. Grandparents take more responsibility for child care Mother sobs over grave of her 6 th child dead from typhoid. Large number of elderly people at Bingo.
Answer The Following... 1.Describe the population of each pyramid and suggest reasons for their shape. 2.Suggest ideas for each pyramids population momentum (How each would look in 25 years time). 3.Give a list of reasons (at least 5 per pyramid) to explain benefits and problems of their population projection.
25 Years Later... Look at the 2 population pyramids for 2025 and compare them to your (2000) projections. Is what you see, what you expected?