AGEC International Economic Development Course slides for week 4 (Feb. 2 & 4) Population growth and demographic transition* What determines changes and differences in population growth, and in the proportion of people at each age? * If you’re following the textbook, this material is in Chapter 4.

Some terminology: Demography and economics The English language can be very confusing! When talking about… “demography”: study of population, also the population itself “population growth”: increasing number of people “demographics”: measured characteristics of the population “ But also… the “economy”: the prod. & cons. activities of a population “economic growth”: increases in prod. & cons. per person “economics”: a way of studying the economy

Population Growth Over Time Our Textbook Picture:

Population Growth Across Countries Our Textbook Picture:

Is population growth a problem… …or an opportunity? Pop. growth lowers the amount of available land and other kinds of capital per person, …but it raises the total size of the economy, which may offer some benefits of scale:  more opportunity to specialize & trade  more innovators with new ideas  a larger market to cover fixed costs on balance, pop. size itself is not really bad; but changes during transition can be awful!

Famine in China, : with quick catch-up afterwards! Fast rise Slow fall meanwhile, in the richer countries

What drives population growth? The “demographic transition”: –population growth rates rise and then fall …but what happens during the transition? –What initiates the change? –Do all countries follow the same path? –What determines the speed of change?

What happens during demographic transition? Our textbook picture is:

So what drives population growth is: The “demographic transition”: –population growth rates rise and then fall –driven by a decline in the death rate –the “mortality transition” –followed by a decline in the birth rate –the “fertility transition” Do all countries follow the same path?

Here’s the demographic transition for one specific country: Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at Crude Birth Rate (CBR): births per thousand people Crude Death Rate (CDR): deaths per thousand people what type of country is this? what caused these changes?

Each year’s “natural increase” in a population is their total births minus total deaths Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at Crude Birth Rate (CBR): births per thousand people Crude Death Rate (CDR): deaths per thousand people How fast is population growth?

That was Sweden… Death rates began to fall after 1800 –fell gradually from per thousand –stopped falling at 10 per thousand in 1955 Birth rates began to fall after 1825 –fell gradually from per thousand –reached death rate of 10 per thousand in 1980 Pop. growth went from 0.5 to 1.0 to zero pct./yr

And here it is again, in comparison with another country: Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at what type of country is this one? The first country is Sweden… the second is Mauritius, an island off the coast of Africa

Population growth rates depend on both birth and death rates Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at Mauritius had very fast population growth after WWII, because of a very rapid decline in its death rate How fast was Mauritius’s peak rate of population growth? When was it?

Fast mortality decline after WWII was driven by public health breakthroughs in many tropical countries Reprinted from D.E. Bloom and J.G. Williamson, “Demographic Transitions and Economic Miracles in Emerging Asia.” World Bank Economic Review 12(3):

…but now let’s compare Sweden to a different country: Sweden--Birth Rate Sweden--Death Rate Sources: Population Reference Bureau ( Underlying data are in 5-year intervals, from B.R. Mitchell, European Historical Statistics (1976): table B6; Council of Europe, Recent Demographic Developments in Europe 2001 (2001): tables T3.1 and T4.1; CELADE, Boletin demografico 69 (2002): tables 4 and 7; F. Alba-Hernandez, La poblacion de Mexico (1976): 14; and UN Population Division, World Population Prospects: The 2002 Revision (2003): 326. ??--Birth Rate ??--Death Rate

Remember, population growth rates depend on both birth and death rates Sweden--Birth Rate Sweden--Death Rate Sources: Population Reference Bureau ( Underlying data are in 5-year intervals, from B.R. Mitchell, European Historical Statistics (1976): table B6; Council of Europe, Recent Demographic Developments in Europe 2001 (2001): tables T3.1 and T4.1; CELADE, Boletin demografico 69 (2002): tables 4 and 7; F. Alba-Hernandez, La poblacion de Mexico (1976): 14; and UN Population Division, World Population Prospects: The 2002 Revision (2003): 326. ??--Birth Rate ??--Death Rate How did this country’s birth rate stay high for so long? How did that affect their population growth?

Africa’s demographic transition started late, and had a very high peak population growth rate Source: Calculated from data in FAOStat (2007).

So what explains the historical mortality decline in today’s rich countries? Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at what kinds of disease are these? when were they reduced? The first measles vaccine was introduced in 1968, way after the disease stopped causing many deaths

An example of mortality decline in the US Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at

Within the U.S., whose mortality declined the most?

The 1918 flu epidemic was unusual in many ways: normally, mortality changed most for children

Another view of mortality by age Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at

The HIV/AIDS epidemic is unusual in many ways: one complication is that it affects mainly adults Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at Great Britain Botswana Niger 17 th C. England

The demographic transition involves both mortality and fertility Mortality rates fall due to better nutrition, public health conditions, medicines… What happens to fertility rates? –How high are the highest fertility rates?  biological maximum is around 12  economic maximum is around 8-10 –How low are the lowest fertility rates?  biological minimum is zero  replacement fertility is around 2

Birth rates depend on both fertility (births/woman) and the number of women Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005 Reprinted from Population Reference Bureau, 2007 World Population Datasheet. (

Fertility rates don’t always fall! Average number of children per woman Source: United Nations, World Population Prospects: The 2004 Revision, Reprinted from Population Reference Bureau ( Uganda Kenya Colombia South Korea Fertility Trends in Selected Developing Countries,

…and they vary in rich countries too! Source: National statistical agencies.. Reprinted from Population Reference Bureau, 2007 World Population Datasheet. ( Fertility Trends in Europe and the United States:

The fertility transition is usually from 6-8 to 1-3 births per woman What can explain this regularity? Why do the poor have more kids than the rich? –why might they choose higher fertility on purpose?  poorer women may have fewer other options  their children may be more valuable to them  poorer children start work at a younger age  …and may help parents in old age or sickness  where child mortality is high, parents need to have many children to have some survive –availability and ease of contraception matters too!

One explaination for fertility decline is lower infant mortality Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at

Fertility decline versus infant mortality across countries Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at

Fertility decline vs. infant mortality over time Source: Montgomery, Keith (2000), “Notes on the Demographic Transition.” Available online at

The demographic transition affects more than population growth How does transition affect the mix of people? –Death rates fall mainly for children –Fertility rates fall later and more slowly  so the burst of population growth takes the form of more surviving children

Demographic transition and age structure: your textbook “population pyramid”

Demographic transition and age structure: the population pyramid for Nigeria 1980 Reprinted from

Demographic transition and age structure: the population pyramid for Nigeria 2000 Reprinted from

Demographic transition and age structure: the population pyramid for Nigeria 2020 This helps explain your results from Exercise 1! Reprinted from

Demographic transition and age structure: population pyramids for Indonesia 1980 Reprinted from Indonesia has a much more “mature” population pyramid than Nigeria

Demographic transition and age structure: population pyramids for Indonesia 2000 Reprinted from Indonesia has a much more “mature” population pyramid than Nigeria

Demographic transition and age structure: population pyramids for Indonesia 2020 Reprinted from Indonesia has a much more “mature” population pyramid than Nigeria

Demographic transition and age structure: population pyramids for the United States 1980 Reprinted from The population “ages”, but there are continued echoes of the post-WWII baby boom

Demographic transition and age structure: population pyramids for the United States 2000 Reprinted from The population “ages”, but there are continued echoes of the post-WWII baby boom

Demographic transition and age structure: population pyramids for the United States 2020 Reprinted from The population “ages”, but there are continued echoes of the post-WWII baby boom

Demographic transition and the age structure of the population During the demographic transition, when death rates fall before and faster than birth rates, –at first kids are an increasing share of the population, so the “dependency ratio” rises –then kids are a decreasing proportion of people, and the share who are working rises –eventually share who are elderly rises, and the proportion who are working falls again

Source: UN Population Division, World Population Prospects: The 2000 Revision ( Past and Projected Child Dependency Changing age structure has a big influence on the economy No. of children (0-14) per 100 adults (15-59) E. AsiaS. AsiaSub-Sah. AfricaWhole World

The demographic transition to higher and then lower population growth rates… –starts with a decline in child mortality  due historically to better nutrition and living conditions, and then to medical intervention –is completed by a decline in fertility  due mainly to increased child survival, increased investment in child’s education, reduced need for child’s work, and increases in mother’s other opportunities In conclusion...

…demography is very important! –in Europe death rates fell slowly, in response to slow improvements in standard of living; –in Africa, Asia and Latin America, death rates fell quickly with sudden availability of vaccines, antibiotics and disease control after WWII –so today’s poor countries have had much faster pop. growth and worse dependency ratios than Europe or America ever did