5th chapter research methods

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Copyright © 2013 Pearson Education, Inc. Publishing as Addison-Wesley

FUTURE

POPULATIONTRENDS

Chapter 5

Marco Savioli




Future population trends

Population’s age structure (fraction of the population indifferent age groups) affects income per capita

The size of world’s population is important for the amountof natural resources available to each person and world-scale environmental problems such as global warming

We can make fairly accurate guesses about populationgrowth over the next 20 or even 50 years

In the developed countries, the fraction of nonworkingelderly will rise imposing economic burden

Many developing countries will receive a «demographicgift» as population growth slows and the fraction of thepopulation made up of children falls




5-3

Figure 5.1 World Population, 1850 –2150

UNforecast:worldpopulationwill stabilizeat 11 billionsometimearound theyear 2200




5-4

Figure 5.2 Population Forecasting

Breakdown of thepopulation into thenumber of people of eachage in a particular year

To forecast the next year,we «age» the population,making an adjustment formortality

Survivorship function

gives information on thelikelihood of survival

Same calculation todetermine the number ofpeople in all other agegroups; for those agedzero, age-specific fertilityrate applied to thenumber of women ineach age group

Summing up and carryingforward year by year thisprocess gives population

forecasting (also accountfor immigration andemigration)




Forecasting mortality

Improvements in mortality significantly raised the net rateof reproduction (NRR)

In forecasting future changes in population growth,mortality changes are likely to have much less effect sincethe fraction of girls living through their childbearing years

is already close to 100% Potential improvements in life expectancy will have a fairly

small effect on the NRR

If the number of births does not change but people livelonger, more people are alive at any given time

Improvements in mortality less important than changes infertility in determining population growth




Forecasting fertility

Forecasts of fertility are made relative to replacementfertility – the level of fertility consistent with aconstant population size in the long run

Even in the most developed countries, there is some

mortality before women’s childbearing years, andslightly more boys are born than girls → TFR

consistent with zero population growth is 2.1

UN predicted in all the countries in the world TFR

would move toward replacement fertility over thenext 50 years (TFR = 2.1 by the year 2050); a sharpfall for developing and a significant rise for developed




5-7

Figure 5.3 Total Fertility Rate in Japan: Actual

versus Forecast

Difficultyin

forecastingfertility:pastforecastsfared notso good




Fertility in rich countries

2009 OECD TFR= 1.74; however, broad variation:

USA TFR = 2.05

Ita TFR = 1.41

Spa TFR = 1.40

Jap TFR = 1.37

Ger TFR = 1.36

SKr TFR = 1.28

In absence of large-scale immigration, low fertility rates

will translate into shrinking populations

Low fertility will also raise average age of the population




5-9

Table 5.1 Fertility in the Developing World




5-10

Figure 5.4 Income per Capita versus Total

Fertility Rate




Demographic momentum

If the number of women in their reproductive years rises(after a period of population growth), then the number ofbabies born also will rise

Even if fertility falls, the number of babies born will rise,for the simple reason that the number of women in theirreproductive years will continue to rise

Only after several generations will the effect of thisdemographic momentum wear off, at which point thegrowth rate of population will be zero

A useful measure of the demographic momentum is thefraction of the population under age 15

Over the very long run, the most important determinant ofpopulation growth will be fertility, about which we havelittle theoretical basis for speculating




5-12

Figure 5.5 The Great Spike in World

Population Growth (W. W. Rostow)

Rostowhasassumedthat the200 yearsafter thepopulation growthpeak willsee asymmetri

creduction

Instead ofthe greatspike, agreat stepinpopulation growthispossible

Or

negativegrowth…




5-13

Table 5.2 Average Annual Growth Rates

of Population by Country Group




The economic consequences ofdemographic change

The growth of world population over the period 2000-2050 (0.9% per year) is forecast to be only half asrapid as over the previous 50 years (1.8% per year)

What is the effect of demographic change oneconomic growth?

We can examine these economic effects by applyingthe Solow model, extended to accommodatepopulation (two points in time for a single country)

=

+

+

(−)




The economic consequences ofdemographic change

Case of the less developed countries (population growthrate forecast to fall from 2.1% to 0.8%) and plausiblevalues = 0.05, = 1 3.

=0.021 + 0.05

0.008 + 0.05

≈ 1.11

A slowdown in population growth, by reducing the effect ofcapital dilution, will raise the pace of economic growth

However, the level of population will continue to rise. More

people will lead to fewer natural resources per capita andthus to a negative effect on the level of output per capita




5-16

Figure 5.6 Changes in the Age Structure of

the Population, 1950 –2050

One of the mostimportant ongoingdemographicchanges is the agingof the world’spopulation

Over the period2000-50, themedian age of theglobal population isforecast to rise from

26.5 to 36.2 years(declining mortalityand fertility)




Population aging

Throughout the world there is an ongoing decline inthe fraction of population made up of children and anincrease in the fraction made up of the elderly

But the timing of this restructuring differs among thegroups of countries

in the more developed, by 2050 there will be 1.7times as many elderly people as children

in the less developed, by 2050 children will stilloutnumber the elderly

in the least developed, by 2050 the elderlyfraction of the population will still be only 7%




Population aging

When we think about how productive a country is, it isoften natural to focus on GDP per worker

When we ask how well off a country is, a more relevantmeasure is the output that is available for every person inthe economy, that is GDP per capita

=

=

= ×




5-19

Figure 5.7 Working-Age Fraction of the U.S.

Population, 1950 –2050

2000-2050

Mostdevelopedcountries:%population

15-64 from67% to 59%

Leastdevelopedcountries:

%population15-64 from54% to 65%

1950s: thepostwar babyboom raisedthe fractionof the

populationmade up ofchildren

1965-85:babyboomersentered thelabor force




Population aging

= income per capita, = income per worker, =fraction of the population that is of working age

= × → → = +

Decline in the fraction of the working-age population in theUS over the period 2010-30: from 0.60 to 0.54

=0.54

0.60

1 ≈ 0.5%

The demographic change will reduce the growth rate ofGDP per capita in the US by 0.5% per year

In addition, as society ages crime rates may fall, butyoung people account for much of a society’s dynamism




5-22

Figure 5.8 Distribution of the World’s

Population

Americassuffered theEuropean

«discovery»; since 1800massiveimmigrationandeconomicgrowth

Europe andAfricaexchangedtheir

positions:1900Europe’spopulation3 timesAfrica’s;2050 theopposite




Redrawing the world map

In addition to these intercontinental redistributions ofpopulation, there will also be changes in countries’relative populations

The countries expected to have the most populationgrowth are also the poorest. Thus, the fraction of the

population that will live in countries that are now richwill fall over time

The UN forecasts that the share of world populationliving in the currently more developed regions willdecrease from 20% to 13% (period 2000-50),whereas the fraction living in the currently leastdeveloped countries will increase from 11% to 20%




5-24

Table 5.4 The Composition Effect




Redrawing the world map

The reason that the average level of GPD per capita inthe world does not grow as quickly as the average ineach country is that the balance of population isshifting toward poorer countries (composition effect)

The fact that the fraction of the world’s populationliving in currently rich countries will fall does notmean that the fraction of the world’s population livingin rich countries will fall

More countries are becoming rich over time. Thus, the

overall balance between rich and poor people in theworld depends on which force is more powerful




Going for the gold

Olympics may measure the outcome of internationalcompetition affected by relative population sizes

Both high income per capita and high populationshould raise a country’s medal count

In rich countries citizens have more time to devote toathletics, better facilities for training, better health

High-population countries have superior athletes

Reasonable approximation is a country’s total GDP

Also, aging population has a negative effect

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