be explained by the equally impressive decline in youth dependency burdens. Wherever the youth dependency burden has fallen dramatically, Asian countries have relinquished their reliance on foreign capital.‖ They found this effect to be stronger in East Asia than in South Asia, where the fertility transition has been less rapid.

Bloom and Williamson (1998) argued that rapid fertility decline in East Asia facilitated the rapid economic growth in this region by reducing the dependency ratio, ―thereby expanding the per capita productive capacity of East Asian economies‖. They noted that this is a temporary window of opportunity, because continuing fertility and mortality decline will result in high proportions of old people relative to working-age adults. They also pointed out that the East Asia region was able to capitalize heavily on this opportunity because they had built the policy and institutional settings needed to realize the growth potential created by this demographic dividend.

The gains from this demographic window of opportunity may be made permanent if they are invested in physical capital and human capital (Lee 2009). With good planning, this demographic dividend can be used to transform economies such that their growth potential remains high after the window has closed.

Moving to global macro-studies, Kelley and Schmidt (2005) conclude that higher dependency ratios (including both youth and old-age dependency ratios) have a significant impact on growth. They find that ―Worldwide, the combined impacts of demographic change have accounted for approximately 20% of per capita output growth impacts, with larger shares in Asia and Europe.‖ Earlier, they had found that dependency ratios impact on savings, from an examination of 65 less developed countries and 23 developed countries over time and cross-sectionally since 1960 (Kelley and Schmidt 1996).

Turning to the question of whether rapid population growth reduces growth in income per capita, Acemoglu and Johnson (2007) examine the data from 47 developed and developing countries over the period 1940-2000 and conclude that ―Overall, the increases in life expectancy (and the associated increases in population) appear to have reduced income per capita.‖ (Acemoglu and Johnson 2007: 975).

As Galor and Weil (2000: abstract) put it, the relationship between population growth and income growth changes as economies mature: ―The economy evolves from a Malthusian regime, where technological progress is slow and population growth prevents any sustained rise in income per capita, into a Post-Malthusian regime, where technological progress rises and population growth absorbs only part of output growth. Ultimately...the economy enters a Modem Growth regime with reduced population growth and sustained income growth‖.

# **_2.5  What of poverty reduction?_**

Although the debates summarized here have focused more on the potential impact of population dynamics on economic growth rather than explicitly on poverty reduction, it is apparent that they view economic growth as a means to raise living standards and reduce poverty. GDP growth ― whether derived from growth in the agricultural, manufacturing, or service sectors ― typically raises living standards among substantial sections of the population, with ripple effects for others. A possible exception is growth that derives from exploitation of mineral resources (such as oil), where small elites can potentially capture much of the proceeds.

Some micro-studies have focused on fertility and children‘s wellbeing. They support Coale and Hoover‘s thesis that at the household level, high fertility reduces investments in children. Some studies use twin births to minimize the potential confounding effect of endogeneity: namely, that parents who have larger numbers of children have different characteristics from those who have few children. Using this method, Rosenzweig and Wolpin (1980:239) found that in India: ―exogenous increases in fertility decrease child quality and suggest that a decrease in family size brought about, say, by exogenous improvements in birth 6