| English | 意味 |
|---|---|
| population/ˌpɒpjʊˈleɪʃn/ | 人口 |
| immigration/ˌɪmɪˈɡreɪʃn/ | 移入 |
| emigration/ˌemɪˈɡreɪʃn/ | 移出 |
| birth rate/bɜːθ reɪt/ | 出生率 |
| death rate/deθ reɪt/ | 死亡率 |
| ageing population/ˈeɪdʒɪŋ ˌpɒpjʊˈleɪʃn/ | 高齢化社会 |
| optimum population/ˈɒptɪməm ˌpɒpjʊˈleɪʃn/ | 適正人口 |
More mouths, more hands
- The number of people in a country — and their ages — shapes everything from schools to pensions.
- Economists study how and why a population 人口 changes.
Development chain lab
Follow how policy and resources can change living standards.
A country's population rises when:
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Natural increase plus net migration drives growth.
The number of births per 1000 people per year is the birth ______.
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Birth and death rates are measured per 1000 per year.
Why population changes
- Population rises when births + immigration 迁入 exceed deaths + emigration 迁出.
- The birth rate 出生率 and death rate 死亡率 are measured per 1000 people per year.
Worked example. In one year a country has 800,000 births, 500,000 deaths, 300,000 immigrants and 100,000 emigrants. Natural change = 800,000 − 500,000 = 300,000; net migration = 300,000 − 100,000 = 200,000. Total population change = 300,000 + 200,000 = +500,000.
Population pyramids of a developing and a developed country
Population grows when births exceed deaths
An ageing population is likely to increase the cost of:
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More elderly people raise pension and healthcare spending.
Age structure
- A young population (high birth rate) needs many schools and creates a future workforce.
- An ageing population 人口老龄化 (longer lives, fewer births) raises the cost of pensions and healthcare.
A country's population grows when births plus immigration are greater than deaths plus emigration
The optimum population is the one that:
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It makes the best use of resources — highest output per head.
Over-population means too many people relative to available resources.
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It is about the people-to-resources ratio, not absolute numbers.
Optimum population 适度人口
- The optimum population makes the best use of resources — the highest output per head.
- Too few people (under-populated) or too many (over-populated) both lower output per head.
Over-population isn't just "too many people". It means too many relative to resources. A small country can be over-populated and a huge one under-populated — it depends on resources, not size alone.
An ageing population means fewer workers per retired person, more spending on pensions and healthcare, and pressure for higher taxes or migration
You've got it
- population rises when births + immigration exceed deaths + emigration
- a young population strains schools; an ageing one strains pensions/healthcare
- the optimum population maximises output per head for given resources