The preceding projections indicated that, even with rapid fertility declines, population growth in Pakistan will continue for some decades. The expected future growth is attrib- utable to four main demographic factors (Bongaarts 1994; Bongaarts and Bulatao 1999). We discuss these below.
FIGURE 2.4 Population size 1950–2010 and projections 2010–2050 for three age groups
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 0 20 40 60 80 100 120 140 160 180 200 Million 15–64 years 65+ years
SOURCE: Population Council 2011.
CAPTURING THE DEMOGRAPHIC DIVIDEND IN PAKISTAN
high fertility
Fertility will be considered “high” if it exceeds the replacement level of 2.1 children per woman. Replacement is a critical factor in population dynamics because it equals the fertility level that, if maintained over time, produces zero population growth. Positive deviations from replacement lead in the long run to persistent population growth, while negative deviations lead to decline. Currently, replacement fertility equals 2.3 births per woman in Pakistan (this level exceeds 2 because children who die before reaching the reproductive ages have to be replaced with additional births).
Fertility in Pakistan has been above replacement for most of its history, with levels approaching 7 births per woman in the 1960s, declining to around 6 in the 1980s and to its current level of 3.7. As shown in Figure 2.2, the PC projection assumes that fertility will decline further in the future, eventually stabilizing at 2 births per woman in the long run. Because current and projected levels are above replacement, high fertility will re- main one of the key forces contributing to further population growth until replacement fertility is reached.
Declining mortality
Rapid declines in mortality have been the main cause of population growth in the past. Since the middle of the twentieth century, Pakistan has experienced exceptionally rapid improvements in life expectancy, rising from 41 years in 1950–55 to 65 years today. These improvements are in large part due to the global spread of medical and public health technology (e.g., immunization, antibiotics), rising standards of living and nutri- tion, and improved medical care after World War II. Over the next 40 years, projections assume that life expectancy will continue to rise, reaching 72 years in 2050. Thus the impact of mortality decline will continue.
Population momentum from a young age structure
Even if fertility were immediately lowered to the replacement level, population growth would continue in most countries in the developing world. The reason for this is a young age structure, which is the result of high fertility and rapid population growth in recent decades. With a large proportion of the population under age 25, further growth in the coming decades is assured. The relative abundance of these young people results in a birth rate that is higher than the death rate even if fertility is at replacement. This effect on future growth is called population momentum.
The effect of population momentum can be reduced significantly if young people marry later and delay their first birth. In addition, the likelihood is that young people in Pakistan will have smaller families than earlier generations, but not uniformly. Better-educated young people, especially women, are likely to have much lower fertility than their parents, but uneducated youth will deviate less from their parents’ behavior.
migration
International migration can significantly affect population growth in some countries (e.g., into the US, and out of other countries, e.g., Mexico), but it often has a very small demographic impact in others. For Pakistan the net flow of out-migration is estimated at 1 per 1,000 population. This makes migration a very small component, only slightly slowing population growth. The forthcoming census is expected to give a better idea of both in-migration from neighboring countries and out-migration, particularly to the Middle East.
A full analysis of the contribution of each of these four demographic factors to future population growth will not be attempted here. Instead, we focus on the contribution of high fertility. To assess the role of high fertility we compare two projections:
1) The standard projection (Population Council 2011), which is determined by all four factors. It includes the effect of high fertility.
2) A hypothetical replacement projection, which is identical to the standard projection except that fertility is set to the replacement level from 2010 onward. This projection excludes the effect of high fertility.
Figure 2.5 presents these two projections for Pakistan. From a baseline level of 174 million in 2010, the standard projections yield a population of 302 million in 2050. In contrast, the replacement projection yields a population of just 264 million. The differ- ence between these projections measures the impact of high fertility, measured in abso- lute terms as 38 million or in relative terms as the percent increase in population due to high fertility (12.5 percent).
FIGURE 2.5 population growth componentsAlternative population projections for 2005–2050 and
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 0 50 100 150 200 250 300 350 400 Million
SOURCE: Population Council 2011.
Standard projection Replacement projection Effect of: Momentum High fertility
CAPTURING THE DEMOGRAPHIC DIVIDEND IN PAKISTAN
Even with instant attainment of replacement fertility, the population of Pakistan is still expected to grow by 53 percent (an addition of 91.7 million) over the next four decades. More than half of all population growth between now and 2050 is attributable to the momentum inherent in the country’s young age structure (the effects of mortality and migration are small and offsetting). This growth represents the children who will be born to parents currently aged under 30 and will be influenced by marriage timing and wanted and unwanted fertility of that group.