household income. Rapid population growth will initially increase the depend-
ency burden (defined as the ratio of the population under 15 and over 64 to the
population of working age) by increasing the relative number of children. In
Nigeria, for example, around half the population are under 15. In developed
countries the dependency burden is instead the result of declining fertility and
mortality, leading to a relative increase in the population aged over 64. In
Sweden 20 per cent of the population are over 65. Either version of depend-
ency will place a greater demand at the aggregate level through taxation and at
the household level on those working to finance the consumption needs of the
non-working. Dependency burdens may be less relevant in the poorest devel-
oping countries where children can enter the labour force at an early age and
older people continue working and are less likely to take up golf at 65.
Some scholars have suggested that rapid population growth causes defor-
estation and desertification, as people are pushed onto marginal land to sustain
subsistence production. This argument misses the real causal chain. The true
drivers of environmental problems are changing demand patterns from the
wealthy (recall the discussion of changing diets in Chapter 1) to a more meat-
intensive diet (which can lead to clearance of land for farming), or technology
(the chainsaw,not an impoverished peasant, most ruthlessly clears forest) and
inequality (the average US person consumes 350 times as much energy as the
av erage Ethiopian). This last point is supported by Molinas (2010), who sepa-
rates the impacts of population growth, economic growth and technology on
carbon emissions in India between 2003 and 2030 (which he forecasts will
double during these dates). Population growth will play a relatively marginal
role. Population growth, he forecasts, will account for just 26.83 per cent of
total increase in CO 2 emissions. The fast growth of the Indian economy is the
main cause, accounting for 131.7 per cent of the increase in CO 2.
Technological change is likely to offset 58.53 per cent of the increase in CO 2
until 2030. He notes that population growth in China will contribute less than
10 per cent of the increase in Chinese CO 2 emission over the same period.
Population growth and the economy: the positive
Population growth can benefit economic growth. Ester Boserup (1965) argued
that population growth can stimulate technological change. She argued that a
dense population was needed to utilize modern transport facilities, provide
labour for labour-intensive rice-based agriculture, and provide all the develop-
ment benefits of urbanization. Models of ‘endogenous technological change’
have shown how higher population growth spurs technological change
(Grossman and Helpman, 1991; Aghion and Howitt, 1992). They have given
mathematical and theoretical rigour to the earlier arguments of Boserup. This
result comes from the non-rivalry nature of technology which means that the
cost of inventing technology is independent of the number of people using it,
whilst the likelihood of invention increases with the population (and conse-
quent number of inventors).
82 Sources of Growth in the Modern World Economy since 1950