d.Class Notes #15

Why is global population increasing?

• Population structure (continued).
• Sex ratio.
• Number of males per 100 females in the population.
• Developed countries have more females than males because they tend to live 7 more years).

Why does population growth vary among regions?

• Demographic transition.
• Helps to explain the rising and falling of natural increase over a period of time in a country.
• There are 4 stages from which there is no coming back.
• So it can be thought of having a beginning, a middle, and an end.
• 1.  Low growth.
• Very high birth and death rates that make no long-term natural increase.
• 2. High growth.
• Rapidly declining death rate and very high birth rate which results in a high natural increase.
• Europe and Northern America entered stage 2 as a result of the Industrial Revolution (around the 1750s).
• Africa, Asia, and Latin America entered stage 2 nearly 2 centuries after Europe and Northern America as a result of the medical revolution, when medical care improved.
• 3. Moderate growth.
• Rapid decline in birth rate and a steady decline in death rate.
• Natural increase is moderate.
• Gap between crude birth rate and crude death rate is narrower than in stage 2.
• But population still grows since the crude birth rate is greater than the crude death rate.
• Most European countries entered stage 3 since the start of the 20th century.
• 4. Low growth.
• Very low birth and death rates.
• No long-term natural increase (possibly a decrease).
• A country reaches stage 4 when the population gains by crude birth rate diminish because of the crude death rate.
• When that happens, it is called zero population growth (ZPG).
• Also defined as total fertility rate that produces no population change whatsoever.
• When a country is at stage 4, their only population change comes from immigration.