population

Population

Key Issue 3

Deep Thought

• What can be determined about the following places based on their population pyramids?

Geographic Models – always remember models are just models – not reality

GEOGRAPHIC MODELS

• First, Models are JUST models• Discuss the purpose of the model. What does

the model do?• Basic assumptions of the model• Description and analysis of the model (zones)• Usefulness and/or applications of the model

Demographic Transition Model

• The process of change in a society’s population from a condition of high crude birth and death rates and low rate of natural increase to a condition of low crude birth and death rates, low rate of natural increase and a higher total population.

• Barring catastrophe, the transition is irreversible!

Stage 1: Low Growth

• CBR and CDR varied considerably from one year to the next but were at very high levels.

• NIR was essentially zero.• During this stage people depended on hunting and

gathering until 8000 B.C. when the agricultural revolution gave people more stable sources of food.

• But food supplies were still unpredictable and war/disease also took their toll in stage 1 societies – thus low growth occurred (about half a million people).

• No country is still in Stage 1

Stage 2: High Growth• Around A.D. 1750 the world’s population suddenly began to grow

10 times faster than in the past.• High growth occurs because the CDR drops and while the CBR

remains roughly the same, thus leading to a high NIR.• Countries entered stage 2 as a result of the Industrial

Revolution (began in England and spread to Europe/North America).

• Industrial Revolution led to increases in wealth = increases in health.

• Greater improvements to agriculture, sanitation – water and sewage.

• Africa, Asia and Latin America did not enter stage 2 until the 1950’s.

• Countries in Africa, Asia, and Latin America moved into stage 2 during the second half of the 20th century due to the medical revolution. Diffusion of medical technology from Europe and North America impacted CDR.

Stage 3: Moderate Growth

• A country moves into stage 3 when the CBR begins to drop sharply.

• Population continues to grow because CBR is still higher than CDR but the NIR is lower than stage 2 countries.

• European and North American countries moved into stage 3 during the first half of the 20th century and recently most countries in Asia and Latin America have moved into to stage 3.

• Most African countries remain in stage 2.• Societies enter stage 3 when people CHOOSE to have fewer

children = decline in IMR, economic changes from rural to urban.

Stage 4: Low Growth

• Countries reach stage 4 when CBR declines to the point where it equals CDR, and the natural increase rate approaches zero.

• Stage 4 countries enter zero population growth (ZPG).• TFR of approximately 2.1 produces ZPG.• Women in stage 4 countries enter the workforce, creating changes

in lifestyle leading to smaller families.• Also, government policies of former communist countries led to

lower CBR and higher CDR’s.• Negative NIR rates mean that CDR exceeds CBR and if it

continues may lead to a future stage 5 of the Demographic Transition.

Do the DEMOGRAPHIC TRANSITION… Explain each stage as a class

• Based on Western Europe’s experiences

• Stage 3 - personal choices – most critical stage

• Stage 4 – social customs - women

Now, let’s apply the model

Questions for the DTM Stage Descriptor

Billy loses his job as a grave digger Parents start to think more about family planning Children are warmer in bed at night because they have more brothers and sisters There are more Golden Anniversaries Large percentage of women never have a child A mother sobs over the grave of her last six children who died in a typhoid epidemic A lot more houses are being built The Public Health Inspector smiles as the building of sewers are completed Fewer children share a bedroom Grandparents are very rare There are no brothers/sisters, no aunts/uncles, no cousins

Tell us more, Hans!

• Let’s let Hans help explain - 15 min.• http://www.ted.com/talks/hans_rosling_the_good_news_of_

the_decade.html?utm_source=newsletter_weekly_2010-10-12&utm_campaign=newsletter_weekly&utm_medium=email