World Population Trends January 26, 2012 World Population Trends - - PowerPoint PPT Presentation

World Population Trends

January 26, 2012

World Population Trends

World Population Growth 1900-2000

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World Population Growth to 2005

Population 1000 2000 3000 4000 5000 6000 7000 1 1 1 2 1 4 1 6 1 7 5 1 8 5 1 9 1 1 9 3 1 9 5 1 9 6 1 9 7 1 9 8 5 1 9 9 5 2 5 Year

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World Population Growth to 2050

Population

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 1 1 1 1 4 1 7 1 9 5 1 9 2 1 9 5 1 9 6 5 1 9 8 1 9 9 5 2 1 2 2 5 2 4 Year M illions

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Top Ten Cities

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Doubling Times

One way to translate the meaning of population growth rate is to translate it into time it takes the population to double. Let g be the rate of population growth. Then the doubling time, T solves 2 = (1 + g)T ln 2 = T ln(1 + g) ln(1 + g) ≈ g g small T ≈ 0.69 g

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Doubling Times

Doubling Times

100 200 300 400 500 600 1500 1700 1800 1900 1920 1940 1955 1965 1975 1985 1995 2005 2015 2025 2035 2045 Year Years

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Fraction of Ever Alive

How many of people ever alive, are alive today? Figures on population growth suggest that current population represents a large proportion. Not true. Figures misleading as more recent periods shown on graph. Keyfitz and others calculate roughly 8 to 10 percent of people every born are alive today.

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Adults Alive

However, infant mortality rates were high until the twentieth

• century. So many of the people ever born did not survive to

adulthood. If we rephrase the question in terms of adults, then the proportion increases. And with the expansion of education (and especially scientific education), likely it is truth the majority of people who became college professors and engineers are alive today.

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Trends

The textbook reports demographic trends by world region. Straightforward can read on your own. PRB reports by demographic behavior — fertility, contraceptive behavior, mortality, urbanization and immigration. Equally straightforward. Will make selected comments.

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Fertility

In (now) developed countries fertility declined rapidly during the 19th Century, in the US from roughly 7 children 1800 to 4 children in 1900. Fertility declined further and was low during the depression. In the US fertility rose again following WWII. Since the mid-1960s fertility to (in the US) slightly below replacement levels.

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Fertility

Pattern for other developed countries, roughly the same. Secular (long–run) decline with current levels below replacement level. The size and the length of the Baby Boom in the US was larger and longer than in other developed countries (boomlets). And current fertility is higher in the US than in (nearly all) other developed countries.

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Decline before Modern Contraceptives

Important to recognize the large decline in childbearing occurred before the introduction of modern contraceptives (e.g., pill). Hence behavior is important. Even at 7 children, fertility is far below the biological maximum. Hutterites have the highest recorded fertility, many women reporting 16 pregnancies over their reproductive lifetimes.

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Fertility Developing Countries

Here there is more variability across countries. Countries such as (South) Korea has had very rapid decline and its fertility rate is as low as many countries in Europe. Countries in Africa with high fertility rates, birth rates (per 1000 in the population) in the 40s, roughly four times the fertility of developed countries. Highest in Africa, Southern Asia, with fertility levels in Latin and South America in the middle.

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Cohort versus Period

Discussion above and in the readings mix two distinct notions of fertility. cohort A group of people sharing a common temporal demographic experience observed through time. For example, the birth cohort of 1987 is people born in that year. A cohort measure of fertility measures completed fertility.

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Period Measure

Period analysis Observation of a population at a specific period of time. Takes a “snapshot” of the population over a relatively short period of time (e.g., one year). Most demographic rates are from period data and therefore are period rates. Total Fertility Rate is a period measure of fertility. It measures the average number of children a woman would have given prevailing birth rates.

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Family Planning

Family Planning The conscious effort of couples to regulate the number and spacing of births through artificial and natural methods of contraception. Family planning connotes conception control to avoid pregnancy and abortion, but it also includes efforts

• f couples to induce pregnancy. (PRB)

Family Planning Policy — the distribution of modern contraceptives.

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Reproductive Revolution

Use of modern contraceptive methods made it easier and safer to control fertility. Use of BC worldwide rose from under 10 percent of married women in 1960s to about 60 percent in 2003. Debate on role family planning programs in reducing fertility in developing countries since 1960s. India and Indonesia prime examples. PBR reports family planning programs responsible for roughly half the decline.

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Revolution or Development?

Economists frequently give less role to the programs in reducing fertility and attribute the reduction to economic development. That economic development opens opportunities for women and lowers the demand for children. Argument in part centers on whether reduction operates through demand-side or supply-side factors.

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Mortality

Many different measures such as mortality rate (deaths per 1000 population) and life expectancy (at birth and current) Will define concepts when we study mortality, the PRB Handbook provides definitions and discussion. Life expectancy in developed countries is now about 75 to 80

• years. Japan has the highest and life expectancy there is 82 years.

Longer for women than men. And varies in the US by race, lowest for African Americans.

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Life Expectancy Highest and Lowest

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Trend

In Europe and US death rates fell during the 19th Century and through the first–half of the 20th Century. In many developing countries, mortality rates fell sharply after WWII with the diffusion of advances in public health. Improvements in sanitation, water Control and near elimination of infectious diseases.

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Mortality Falls Before Fertility

A common pattern is that mortality rates decline before fertility rates decline. Consequence: population growth

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Largest Gains for the Young

Increases in life expectancy due primarily to reduction in infant and childhood mortality. Rare not to have a sibling die during childhood. In 1790 in the US, life expectancy of someone 30 years old was about what it is today. Before the 20th century in the US among women, child birth was the leading cause of death.

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Impact of HIV/AIDS

The effect of HIV/AIDS in Africa is transparent. 98 percent of HIV/AIDS related deaths in 2003 were in sub–Saharan Africa and other less developed regions. HIV/AIDS reversing many of the gains in health and life expectancy obtained in the last 50 years.

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Migration and Urbanization

Migration within and between countries affects population growth, and the distribution of the population by age, sex and other dimensions. 20th Century movement from rural to urban areas Yet only 18 percent of population in developing countries lived in urban areas in 1950. Increased to 40 percent by 2000. Rapid change.

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Migration and Immigration

Approximately 175 million people are international migrants. (about half the size of the US population) 5 to 10 million people become international migrants each year Most international migrants move from one developing country to another. Most move to take advantage of economic opportunities, but 14 million are refugees

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South to North

Flows from developing to developed countries, labeled as “South to North” From South and Central America and Asia to North America, and from North Africa and the Middle East to Europe. Flows among developed countries relatively small.

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Population Momentum

Ferility, mortality and migration trends reflected in the age and sex profiles of the world’s countries. Fertility has the greatest influence and decades of high fertility in the less developed countries have meant ever–increasing numbers

• f young people.

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Age Pyramids

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Comments on Age Pyramids

Provide a simple graphical device to describe the age and gender composition of a population. Men on the left and women on the right. Percent share of an absolute count is the base while (5–yr) birth cohorts comprise the vertical axis. Several striking features.

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West Africa Pyramid

West Africa — a region with high fertility and mortality. Ravaged by HIV/AIDS. High fertility rate evident in the large base of the pyramid. High mortality rate evident by the sharply declining steps. Also possible to see the effect of differential mortality by sex.

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Western Europe Pyramid

Western Europe — a region with low mortality and very low fertility. Low fertility rates evident by the relative small share of children/youth in the population. Low mortality evident from the large elderly population. As many elderly as there are young! Effect of WWI and WWII evident as well.

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Population Momentum: Example

Consequence of the large base of the West African population is a powerful force for future population growth as the ever–larger cohorts move into childbearing ages. The number of women in childbearing ages in West Africa will roughly triple between 2000 and 2050 (i.e., from 52 million to 151 million). Even if they have fewer children than their mothers did, West African women will produce 11 million births annually during the 50–year period.

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Population Momentum: Definition

Population Momentum is the tendency for population growth to continue beyond the time that replacement–level fertility as been achieved because of the relatively high concentration of people in childbearing ages.

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Western Europe Negative Momentum

The narrow base of the population pyramid in Western Eurpe is a powerful force for “negative momentum.” The number of potential mothers is shrinking from 44 million in 2000 to 36 million in 2050. Even if women in Western Europe have slightly more children than their mothers, the annual number of births is projected to decline, staying below 2 million per year. And with large share of the population that is old, the annual number of deaths will increase, from 1.8 million in 2000 to 2.5 million by 2050.

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Consequence of Momentum

Population growth is virtually certain in West Africa Population will decline in Western Europe unless there is substantial immigration

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Explaining Population Change

Here I (economists) separate company with the demographers. Demographers appeal to proximate determinants. So will ascribe fertility reduction to increased use of contraceptives and abortion. An example is in PRB (2004, p.15)

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TFR Mali vs. Brazil

The vast difference in contraceptive use in Mali and Brazil is the primary reason why Mali’s TFR was 6.8 and Brazil’s TFR was 2.5 in 2003. In Mail, less than 9 percent of women of reproductive age used a contraceptive in 2003, compared to about 76 percent of Brazilian women. (page 15)

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Proximate Determinants

Useful to tell us about the prevalence of contraceptive usage. But what kind of behavioral explanation is it?

World Population Trends

Proximate Determinants

Useful to tell us about the prevalence of contraceptive usage. But what kind of behavioral explanation is it? Contraceptive use is a choice, and a means to an end. Why is the demand for children less in Brazil than in Mali?

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Other factors

PRB also considers the effects

◮ Education ◮ Household income

• n fertility.

Same concern about interpretation.

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Gender Roles

PRB discusses the effect of Gender Roles. Accept their presence. Question of interpretation. Part of individual preferences. Economists take preferences as given. Yet, where does “culture” come from? Why do some societies generate preferences for sons?

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Policy Responses — Fertility

Fertility of central importance for population change. Is it possible for governments to intervene and increase fertility rates? Family policies — subsidize child care, housing, parental benefits. Equal opportunity for women to balance family and workplace demands. Extreme is China’s “One Child” Policy. Largely criticized as regressive and harshly administered.

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Policy Responses — Immigration

Policy can also influence immigration flows. Social planner would move population from West Africa to Western Europe. Solve overcrowding, rapid population growth in Western Africa and the consequences of an aging and declining population in Western Europe.

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Germany shows not so easy

Germany needs 3.4 million immigrants per year to retain a constant ratio of working–age to retired people. From 2003 to 2050 the total number of immigrants needs will be almost 175 million, or twice Germany’s current population. Germany not so keen to see this as a solution.

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Questions for Future

From the PRB (2004)

◮ Will people in Africa, Asia, and Latin America come to prefer

much smaller families now preferred in Europe?

◮ Will developing countries be able to provide family planning

services to impoverished populations?

◮ Will the HIV/AIDS epidemic in Asia and other developing

regions reach the catastrophic levels seen in Southern Africa

◮ Will increased mortality from HIV/AIDS spur families to have

larger families?

◮ Will climate change or environmental degradation threaten

human health?

◮ Will couples in Europe and other low–fertility societies have

more children?

World Population Trends