Population Growth
George Norton
Agricultural and
Applied Economics
Virginia Tech
Objectives
Discuss nature of population growth
in the world
Consider determinants and
consequences of rapid population
growth and urbanization
Population issues to be
discussed
Basic facts about population growth
Consequences of population growth
Causes of population growth
Policies to influence population
growth and rural to urban migration
Has population
increased at a fairly
constant rate since
prehistoric times?
B.C. Today
World Population
Number of Time
People
0 3 million years
ago
300 million 1 AD
500 million 1650
1 billion 1800
2 billion 1930
3 billion 1960
4 billion 1975
5 billion 1987
6 billion 1999
12
11
Past and projected
10
World population
9
8
7
6
5
4
3
2
1
0
1800 1850 1900 1950 2000 2050 2100 2150
World Population
• What is the present
world population?
• What is the current
growth rate and is
the growth rate
currently at its
historical peak?
When would world population double at
the current growth rate?
70/1.2 = 58 years
Is the growth rate likely to remain at
1.2 percent? Why or why not?
Why has population increased
faster in developing countries
today that it did in early stages
of U.S. development?
Are population growth rates more
likely to increase rather than
decrease over the next 10 years?
Decrease
When will the world population stop
growing and at what population?
Maybe in 2150 at 10.5-11.5 billion;
By 2050, expect about 9 billion
Why does population grow when
growth rates are declining?
Recent rapid growth
means young population
with many in child
bearing years
Population pyramid
Let’s examine:
1) Determinants of birth rates
2) Economic factors important in
affecting birth rates
3) Consequences of rapid population
growth
Determinants of birth rates
Income (economic
factors)
Culture and social
factors
Birth control
Education
Religion
Wars
Why are economic factors
important in affecting birth rates?
Children provide labor in agriculture
Children provide social security
Children are a consumption good
Income implies value of time so
number of children
Quantity / quality tradeoff
In what sense is population
growth a substitute for
missing institutions and
markets?
Missing Institutions and markets
Insurance
• Medical
• Life insurance
• Disability
• Natural disaster
• Theft
Social security
• Government
• Employer
Gender bias
Culture and inheritance laws
Low female wages reduces
opportunity cost of children
Education of females
Externalities
What externalities might be involved
with fertility choices and why?
• Costs of certain public goods such as
schools and infrastructure might exceed
private costs
• Environmental effects
• Family structure
What are the consequences of
rapid population growth?
Negative Positive
• Food • Labor
• Difficult to educate • Economies of scale
• Environment • Market
• Age dependency • Intellectual base for
• Jobs ideas and
• Capital shallowing innovations
• Investment • Effect on demand
diversion for technologies
What are some policies that
influence population growth?
Policies for social and economic
improvement
Social security system
Family planning
Female education
Urbanization also increasing
with rural to urban migration
• Nature of migration
• Why migration occurs
• Consequences
• Policy implications
Rural to urban migration
1980’s and 90’s– population growth
in LDC’s averaged 2.1%
But, urban population growth
averaged 3.5% (in many countries, 6
to 8%)
Why is rural to urban migration
good and why is it bad?
Good
• Labor for industry (efficient use of resources)
• Education: costs and benefits
• Larger markets
Bad
• Unemployment
• Housing & Public services
• Environment
Why do people migrate from
rural to urban areas?
Economic factors
• Benefits of move
• Costs of move
• Planning horizon
Social & cultural factors
Who tends to migrate?
Age of migrants?
Young
Education of migrants?
Better educated
Marital status of migrants?
Single
Harris-Todaro Model of
Migration
Potential migrants evaluate the “potential”
or expected gains from migration versus
the costs
Expected gains: real income differential
times the probability of receiving a job
offer
Probability is inversely related to the rate
of unemployment
Migration rates in excess of urban job
growth rates are expected in this model
What is the urban informal
sector?
Why is the informal sector both
good and bad for developing
countries?
What policies can affect rural
to urban migration?
Improve services in rural
areas (education, health,
etc.)
Remove bias in economic
policies
Jobs in rural areas
Conclusions
Population growth and R-U migration
have been rapid in developing
countries in recent years
Many causes but several are
economic and institutional
Effects are positive and negative
Public policies can influence pop
growth and R-U migration rates