2. 2. Population Change Population change is a result of a combination of natural population changes and migration Natural population change can be either in the for of a natural population increase or decrease. It is calculated by calculating the difference between birth and death rates e.g. UK has a birth rate of 12 and a death rate of 9 = Natural Increase 3 per 1000 per annum Angola has a birth rate of 43 and a death rate of 23 = Natural Increase 20 per 1000 per annum Russia has a birth rate of 11 and a death rate of 16 = Natural Decrease 5 per 1000 per annum Birth rate – Death rate = Natural increase / decrease Natural change + or – Migration Rate = Population change
3. 2. Population Change Changes in birth and death rates that were first observed and recorded in the UK – where census records have been kept for longer than any other country. The changes follow a clear pattern where birth and death rates fluctuate over time resulting in very little population change. These fluctuations happened as a result of inconsistent food supplies, the prevalence of diseases, poor living conditions and a lack of food hygiene. Graph shows changes in birth and death rates in Britain over time. Death rates are the first to change as living conditions and health care improves, this created a rapid natural increase around the start of the Industrial Revolution. Birth rates decline later as the need to have large families declines, access to contraception improves and women’s rights improve. In the past 30 years both birth and death rates have been relatively slow and stable resulting in a very small natural increase. This graph was used as the basis for the demographic transition model.
5. Weaknesses: It is based on the experiences of industrialising countries and therefore is not as relevant for non-industrialising countries The model assumes that stage 2 follows industrialisation. In many countries this isn’t the case. The factors that have caused death rates to start falling (medical care and better sanitation) were imported from colonising countries and so arrived far quicker. The model also assumes that stage 3 follows several decades after stage 2. This has often not happened due to a population’s attitude to family size, birth control, status of women and religion. In other cases it happened faster due to government intervention such as in China The original model had to adapted to include a fifth stage as some countries in Western Europe and Japan have experienced changes that have resulted in death rates exceeding birth rates In many African countries death rates have risen dramatically due to diseases such as HIV and AIDS and now appear to be back in stage 1. It is therefore very hard to predict their future Strengths: It is dynamic and shows changes through time It describes what has happened in the UK Many other countries in Europe and North America went through similar stages as they have industrialised Some Newly Industrialised Countries (NICs) such as Singapore and South Korea also seemed to follow a similar pattern, but have done it faster than Britain The model help to explain what has happened and why changes occur over time 2. Application and validity of the DTM
7. 2. Migration and population change Migration is the movement of people from one place to another. The movement can be temporary or permanent. It can happen on a local, national or international scale. The decisions to migrate may be voluntary (e.g. for work) or forced (e.g. to escape war or natural hazards) Migration can have more sudden and dramatic impact on population change than changes in birth and death rates which tend to happen over a longer time scale. This man was caught trying to cross the border between Mexico and the USA concealed inside a bus seat! Migration can also be classified by the distance travelled: Intra-regional: movement within a region e.g. rural to urban or urban to rural Inter-regional: from one region to another e.g. elderly people moving from the Midlands to the South coast to retire International: movement from one country to another e.g. from Poland to the UK The causes of migration can always be explained in the form of push and pull factors
