2 Population ChangesThe total population of an area depends upon changes in the natural increase and migration.The natural increase (or decrease) is the difference between the birth rate and the death rate.The birth rate is the number of live births in a year for every 1000 people in the total population.The death rate is the number of people in every 1000 who die in a year.If the birth rate is higher then the total population will increase. If the death rate is higher then the total population will decrease.
3 The Demographic Transition Model The DTM describes a sequence of changes in the relationship between birth rates and death rates.The model was produced using changes in the natural increase in several industrialised countries in western Europe and North America.It suggests that the population growth rates for all countries can be divided into four stages
4 Demographic Transition Model Total populationBirth rateDeath rateBIRTHS AND DEATHS PER 1000 PER YEARStage 1Stage 2Stage 3Stage 4TIME
5 Demographic Transition Model Total populationBirth rateDeath rateBIRTHS AND DEATHS PER 1000 PER YEARStage 1Stage 2Stage 3Stage 4TIME
6 Stage 1 High Fluctuating Low populationIncreasing very slowlyHigh birth rateHigh death rateEthiopia/NigerUK: pre-1780Birth RateDeath RateTotalPopulation
7 Stage 2 Early Expanding Population growing at faster rate High but decreasing birth rateDecreasing death rateSri Lanka/BoliviaUK:Birth RateDeath RateTotalPopulation
8 Stage 3 Late ExpandingStage 3Population still increasing, but rate of increase slowing downDecreasing birth rateLow death rateUruguay/ChinaUK:TotalPopulationBirth RateDeath Rate
9 Stage 4 Low Fluctuating High population, almost stable Low birth rate Low death rateCanada/USAUK: post-1940TotalPopulationBirth RateDeath Rate
10 What do you think the reasons are for the changes at each stage?
11 Reasons for Stage 1 High Fluctuating Little access to birth controlMany children die in infancy so parents have more to compensateChildren are needed to work on the landSome religions encourage large familiesDeath rates are high due to disease, famine, poor diet, poor hygiene, little medical scienceBirth RateDeath RateTotalPopulation
12 Reasons for Stage 2 Early Expanding Improvements in medical careImprovements in sanitation and water supplyQuality and quantity of food produced improvesTransport and communications improve movements of food and medical suppliesDecrease in infant mortalityBirth RateDeath RateTotalPopulation
13 Reasons for Stage 3 Late Expanding Increased access to contraceptionLower infant mortality rates so less need for bigger familiesIndustrialisation and mechanisation means fewer labourers requiredAs wealth increases, desire for material possessions takes over the desire for large familiesEquality of women means they can follow a career rather than just staying at homeStage 3TotalPopulationBirth RateDeath Rate
14 Reasons for Stage 4 Low Fluctuating Rates fluctuate with ‘baby booms’ and epidemics of illnesses and diseasesReasons for Stage 4 have improved and it stabilisesTotalPopulationBirth RateDeath Rate
15 Stage 5: Depleting Population Is there a Stage 5????Stage 5: Depleting Population
16 Stage IStage IIStage IIIStage IVHigh birth ratesFalling birth ratesLow birth ratesNo or little Family PlanningParents have many children because few surviveMany children are needed to work the landChildren are a sign of virilityReligious beliefs and cultural traditions encourage large familiesFamily Planning usedA lower infant mortality ratesIndustrialization means less need for laborIncreased desire for material possessions and less desire for large familiesEmancipation of womenChildren as liabilities instead of assetsHigh death ratesFalling death ratesLow death ratesDisease and plague (e.g. bubonic, cholera, kwashiorkor)Famine, uncertain food supplies and poor dietPoor hygiene, no clean water or sewage disposalImproved medicineImproved sanitation and waters supplyImprovements in food production in terms of quality and quantityImproved transport to move foodA decrease in child mortality
17 Geographical Variations Developed countriesTook 250 years for most developed economies to go through their own demographic transition (from 1750 to 2000).Population growth never surpassed the capacity of these economies to accommodate it.Developing countriesDemographic transition started in the 20th century:The most advanced segment after WWI.The least advanced segment after WWII.Very few have went trough the transitory mutation.Most of them have a type III demographic transition.By the time they reach type IV, a huge amount a population will be added to their populations.
18 Geographical Variations Will demographic transition occur all around the world?Model based upon the Western experience.Evidence underline that the process is likely.Problems:The base population in the developing world is large.Low percentages of population increase will result in large numbers of additional people.Limited possibilities for immigration (Unlike Europe at the end of the 19th century and early during the 20th century).Religious and cultural influences.
20 Population structures The rates of natural increase, births, deaths, infant mortality and life expectancy all affect the population structure of a country.The population structure of a country can be shown by a population or age-sex pyramid.
21 Population pyramids show The total population divided into five-year age groupsthe percentage of people in each of those age groupsthe percentage of males and females in each age group
22 Population pyramids are useful because they show: Trends in the birth rate, death rate, infant mortality rate and life expectancy - these trends can help a country to plan its future services, e.g. more homes for the elderly if there is an ageing population or fewer schools if there is a declining birth rate.The effects of people migrating into or out of a region or country.The proportion of the population who are economically active and the proportion who are dependent upon them (dependency ratio).