World Population Trends January 26, 2012 World Population Trends
World Population Growth 1900-2000 World Population Trends
World Population Growth to 2005 Population 7000 6000 5000 4000 3000 2000 1000 0 1 5 5 5 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 5 5 3 5 6 7 8 9 0 9 2 4 6 7 8 9 9 9 9 9 9 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 2 Year World Population Trends
World Population Growth to 2050 Population 10000 9000 8000 7000 M illions 6000 5000 4000 3000 2000 1000 0 1 5 5 5 0 0 0 0 0 0 0 0 0 1 0 0 0 5 2 5 6 8 9 2 4 1 4 7 9 9 9 9 9 9 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 Year World Population Trends
Top Ten Cities World Population Trends
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 ≈ 0 . 69 T ≈ g World Population Trends
Doubling Times Years 200 300 400 600 100 500 0 1500 1700 Doubling Times 1800 1900 1920 1940 1955 World Population Trends 1965 Year 1975 1985 1995 2005 2015 2025 2035 2045
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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 of couples to induce pregnancy. (PRB) Family Planning Policy — the distribution of modern contraceptives. World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
Life Expectancy Highest and Lowest World Population Trends
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. World Population Trends
Mortality Falls Before Fertility A common pattern is that mortality rates decline before fertility rates decline. Consequence: population growth World Population Trends
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. World Population Trends
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. World Population Trends
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. World Population Trends
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 World Population Trends
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. World Population Trends
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 of young people. World Population Trends
Age Pyramids World Population Trends
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. World Population Trends
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