2.5 POPULATION STRUCTURE & MEASURABLE CHARACTERISTICS (2.5.A) The structure of a population describes the numbers of people with similar characteristics within a population, e.g. age, gender, ethnicity, religion, socio-economic status, & marital status. Population structure changes over time as people age, but also because of births, deaths and migration. Changes to social, environmental and economic conditions can also influence population structure. E.g., changes in migration reflect a number of factors and have different effects on different age groups. The relationship between population, society, economics and the environment defines a population’s future size and make-up. The structure of a population is best illustrated as a population pyramid
Population pyramid – Bangladesh – what does it tell you?
• Who can use it?
STAGE 1 – EXPANSIVE CONCAVE SHAPE HIGH BIRTH RATE, RAPID FALL IN EACH UPWARD AGE GROUP DUE TO HIGH DEATH RATES • SHORT LIFE EXPECTANCY • SOMALIA • • • •
STAGE 2 – EXPANSIVE PYRAMIDICAL SHAPE STILL HIGH BIRTH RATE FALL IN DEATH RATE AS MORE REACH MIDDLE AGES. • SLIGHTLY LONGER LIFE EXPECTANCY • LARGE YOUTHFUL POP. WILL SOON BECOME ECONOMICALLY ACTIVE. • INDIA • • • •
POPULATION STRUCTURE • STAGE 3 – STATIONARY • DECLINING BIRTH RATE, AS SHOWN BY THE ALMOST EQUAL NUMBERS IN LOWER AGE GROUPS • LOW DEATH RATE • MORE PEOPLE LIVING TO AN OLDER AGE. • ARGENTINA
POPULATION STRUCTURE • • • • • •
STAGE 4 – CONTRACTIVE LOW BIRTH RATE LOW DEATH RATE HIGHER DEPENDENCY RATIO LONGER LIFE EXPECTANCY AS THE NUMBERS ENTERING THE REPRODUCTIVE AGE DECLINE, THERE WILL BE A FALL IN POPULATION SWEDEN, JAPAN Ageing populations Japan
• POP. CAN BE DIVIDED INTO 2 CATEGORIES; • NON-ECONOMICALLY ACTIVE (0-14 & OVER 65) AND ECO. ACTIVE/WORKING POP. (15-65) • THE DEP. RATIO: • 0-14 & 65+/15-65*100= 50-70 IN MEDCs & OFTEN OVER 100 IN LEDCs
• The Demographic Impact of AIDS • Crude death rates eastern/southern Africa as much as 50500 percent greater than without AIDS. • The population growth rate in Zimbabwe has been reduced to nearly zero because of AIDS-related deaths – crude birth rate decreasing • By 2003, there will be negative population growth in Botswana, South Africa and Zimbabwe. Negative population growth has never before been projected in a developing country; it is caused by a combination of high HIV prevalence and declining relatively low fertility. • In the 35 African countries that are highly affected by HIV/AIDS, life expectancy at birth is estimated at 48.3 years, 6.5 years less than it would have been without HIV. The projected population in 2015 is 84 million, 10 % less than it would have been without AIDS. • AIDS mortality is changing the population structure of many African countries. Instead of the "population pyramid" in which there is a gradual reduction in population at higher ages, there is a "population chimney", with a sharp decrease in the number of adults over age 30.
• Germany is experiencing a period of negative growth (-0.1%) – population reduced. • A population can shrink due to a low birth rate and a stable death rate. • Increased emigration may also be a contributor to a declining population.