Population decline was a frequent experience until the nineteenth and twentieth centuries, when population growth became the norm. By the beginning of the twenty-first century, that era of growth was ending. In Europe, population decline is expected to become general by the mid-twenty-first century, and by the end of the century, global population itself may be falling.
Dynamics of Population Decline
Fewer births, more deaths, and net emigration can each provoke population decline: the basic "balancing equation" can be expressed as:
Population Change = Births - Deaths–Net Migration
With modern mortality, where most children survive, each woman needs to produce on average just over two children to replace the population over a generation (25 to 30 years). Average family size is measured by the Total Fertility Rate (TFR), the number of children which the average woman would have over her fertile lifetime (conventionally, ages 15 to 49), given current fertility rates at each age. A TFR of 2.11 implies that women would have, on average, 2.11 children at current rates–1.03 girls and 1.08 boys (assuming the sex ratio at birth to be 1.05). If the female survival rate to the end of the childbearing period is 0.97, women would have, on average, exactly 1.0 surviving daughter to replace them: the Net Reproduction Rate (NRR) is 1.0. Other things being equal, below-replacement fertility–an NRR below 1.0 or, roughly, a TFR below 2.1–implies population decline in the long run.
In the industrial world since the 1970s, and increasingly in the developing world, the TFR has fallen below 2.1 and the NRR below 1.0. Yet most of these populations continue to grow, partly because of immigration (e.g., Germany and Italy). However, most Western countries still have a positive natural increase (excess of births over deaths). Births can exceed deaths for a time, even when the TFR is less than 2.1, if the number of women in their reproductive years is exceptionally high as a legacy of past population growth or bulges such as the "baby boom" cohorts of the 1960s. Only when this structural anomaly ceases will deaths finally exceed births. This delay is known as population momentum. It can sustain growth only for a few decades; the population momentum was ending in most Western populations by the beginning of the twenty-first century (Table 1).
Momentum operates in both directions. A declining population with a structure aged through years of below-replacement fertility would continue to decline in numbers for some years, even if fertility increased to replacement rate (this is the case, for example, in Germany).
Population Decline in the Past
For millennia, until the eighteenth century, average long-term rates of human population growth must have been close to zero. Periods of mild population decline would have been almost as normal as periods of population growth, and except for crisis years, no more perceptible. "Normal" processes served to regulate populations through alternating periods of mild growth and decline, as in early modern Western Europe. There fertility could respond to hard times through delayed marriage, as first described by the English political economist T. R. Malthus (1766–1834).
Deleterious changes (e.g., human mismanagement of resources) can reduce carrying capacity through deforestation or the exhaustion or salination of soils, as in ancient Sumer, the Mayan regions of Central America, and Easter Island. Exogenous climate change helped to eliminate the medieval Vinland and Greenland colonies and almost did the same to Iceland. Other crises were provoked by institutional collapse, new diseases, or warfare, which reduced population irrespective of carrying capacity. Epidemics and famines provoked frequent, sharp but often transient turndowns in population in Europe,
China, India, Japan, and elsewhere. Disease usually kills most of the victims of famine. The destruction by blight of the Irish potato staple in 1846 left 1 million dead. Two million Irish emigrated, inaugurating a new regime of emigration in which Ireland was the only major European area to lose population in the nineteenth century, its size falling from 8 million to 4 million. However, massive famines of the twentieth century, causing population decline if only for brief periods, were mostly the result of human actions: China's Great Leap Forward of 1958–1961 led to some 30 million excess deaths; the Ukraine collectivization famine of 1932 caused 7 million deaths. The globalization of disease can radically reduce population size. Europe's population fell to two-thirds of its previous level after the Black Death of 1348. The Aztec population was at least halved in the sixteenth century, partly through new diseases.
In simple societies, depopulation can result from genocidal conflict. Attrition by nomads on the settled populations in Eurasia suppressed the latter's populations for a thousand years. Europe lost about a quarter of its population in the centuries following the end of the Western Roman Empire, and China may have lost a quarter of its population in its unsuccessful resistance to Mongol invasion in the thirteenth century. The 30 Years War (1618–1648) inflicted similar proportionate losses on much of Northwestern Europe. In the twentieth century, the near-total destruction of Europe's Jews was the worst of a number of genocidal episodes. Enslavement often followed conquest in earlier epochs, but in some cases enslavement was the aim. The effect of slavery on the populations of tropical Africa cannot be known exactly, but in some areas it may have reduced population to a marked degree.
Contemporary Population Decline
As a broad generalization, in the 1930s the developed world reached a two-child family norm. In 2000, the average TFR in the developed world was1.6. The United States is the only developed country with fertility approximately at replacement level. By the turn of the twenty-first century, the developed world also faced population decline. Countries with natural decline (deaths exceeding births) as of 2001 included Italy (-0.08% per year), Germany (-0.09%), most countries in Eastern and Central Europe, and all of the European states of the former Soviet Union. Natural decline is fastest in the Russian Federation (-0.63%), Ukraine (-0.60%), and Bulgaria and Hungary (-0.48%). However, births in France, the Netherlands, and Norway still exceed deaths (their natural increase is over 0.3% per year; in the United States it is 0.3%). Positive natural increase also continues in the United Kingdom, Denmark, and Finland. East of the river Elbe, population decline is exacerbated by persistent high mortality. Population decline in Italy and Germany is only averted by immigration from Eastern European and non-European countries.
Future trends depend primarily on birth rates and migration. According to the United Nations' medium projections made in 2000, France's population is expected to grow to 62 million by 2050 from 59 million in 2000. Germany, however, is projected to decline from 82 to 71 million, Italy from 58 to 43 million, Japan from 127 to 109 million, and Russia from 146 to 104 million. However, it is difficult to accurately predict population change so many years in the future. The low fertility rates in Russia and Eastern Europe in 2000 were deflated by widespread postponement of childbearing, and may recover substantially. By contrast, in the developing world where fertility in many regions is still relatively high, birth rates may not cease to decline once they reach replacement level, as many projections have assumed. But the possibility or even likelihood of global population decline beginning within a century has become accepted by demographers. Figure 1 shows total population estimates and projections from 1950 to 2050.
Political Economy of Population Decline
Fear of population decline, and policy designed to avert it, are almost as old as states themselves. In the distant past, population was, with land, the chief factor of production. Population increase was encouraged, often by means of conquest and enslavement; its diminution to be avoided at all costs. Mercantilist emphasis on population size, even at the cost of individual standards of living, was reinforced by concerns about the size of armies and the security of territory. Some classical economists assumed that Malthusian population checks and diminishing returns imply an early end to economic and population growth, leading to a stationary population. Others, however, including Adam Smith, saw substantial further growth through productivity driven by technology. He saw population growth as desirable: It would expand markets and encourage division of labor. Larger populations permitted economies of scale and increasing rather than diminishing returns, even though resource constraints imposed ultimate limits to growth.
Economic analysis of the consequences of declining population (e.g., the work of William B. Reddaway) began when birth rates first fell to replacement rate in the 1930s. In 2002, conventional economic opinion was almost unanimous in believing that population decline would remove the guarantee of future customers that underwrites future investment, diminish the size of markets, and reduce productive capacity as the workforce falls and as the stimulus for innovation declines. The economist Ester Boserup feared, at the extreme, that some economies would decline to a more extensive, less specialized level. For Julian Simon, population was the "ultimate resource": Fewer people means fewer geniuses.
In Western democracies, France has shown the most consistent policy response to the fear of population decline, nurtured by the stagnation of its population in the nineteenth century. France, which began the nineteenth century as Europe's demographic, military, and economic superpower, ended it just on a par with the United Kingdom and Germany. Near-defeat in the First World War reinforced fears about declining power and population. The official Institut national d'études démographiques
(INED) was set up to analyze population trends and develop effective pro-population policies. Its first director, the demographer Alfred Sauvy (1898–1990), was an indefatigable analyst of the economic and social evils of depopulation and population aging.
With low vital rates, population decline goes hand-in-hand with population aging. The latter, however, provokes different concerns: of excess consumption by an increasing proportion of elderly dependents, rather than the under-consumption arising from population decline feared by English economist John Maynard Keynes.
Other considerations can prevail in crowded Europe. The United Kingdom's Royal Commission on Population (1949) and its Population Panel (1973) felt that the end of population growth would moderate problems of food imports and balance of payments. It concluded that "our analysis … leads to the conclusion that Britain would do better in future with a stationary rather than an increasing population" (Population Panel, p. 6). The Netherlands has long considered itself overpopulated; up to the 1950s it sought, like the United Kingdom, to encourage emigration to ease domestic population pressure. That remains part of the rationale for contemporary policies seeking to discourage immigration. Even in the United States, the 1972 concluding report of the Commission on Population Growth and the American Future saw an end to U.S. population growth–although not a decline–as, on balance, advantageous. Population growth is commonly regarded as a major cause of environmental degradation, the reduction of biodiversity, and the destruction of countryside; on environmental grounds, the prospect of population decline is usually welcomed. An "optimum" population size has been proposed for countries such as the United Kingdom of a third or less of the existing total (20 million). Australian environmentalists, arguing from considerations of sustainable "environmental footprint" (the area of land needed to sustain the current consumption or lifestyle of an individual, community, or country), desire a population for Australia of 10 million, half its 2002 size.
While population decline brings problems, it may be argued that a smaller but stable population has advantages. Problems of overcrowding are ameliorated and the environment is potentially better protected. Unsatisfactory infrastructure, hastily constructed to cope with growth, can be demolished. Labor shortage may reduce unemployment and moderate inequality, and should promote capital substitution as wages rise. Depopulation after the Black Death in Europe helped to end feudalism and ushered in the "golden age of the peasant." With international trade and alliances, markets and security transcend frontiers; in Western Europe there is no relationship between the standard of living and population size or rate of population change. Some European countries have lost territory and (in most cases) inhabitants over the last century (United Kingdom, Germany, Austria), without harming their standard of living. The universal loss of colonies has been a beneficial relief to the former colonizers.
Policies Affecting Fertility and Population
Continental European countries took fright at the below-replacement fertility of the 1930s and instituted wage supplements, loans, and cash benefits to promote family life and the birth rate. In the post-World War II West (except in France), explicit pronatalist measures were discredited by their enthusiastic adoption by pre-war Fascist regimes and were rendered moot, at least temporarily, by the baby boom. Post-war communist regimes in Eastern Europe, faced with rapid falls of fertility, espoused similar policies, which helped to preserve a birth rate around the replacement rate until the collapse of communism. Pronatalist polices to avert impending population decline and moderate population aging in Japan, in Singapore, and elsewhere since the 1970s have so far lacked conspicuous success.
Twenty-first century Western European policies for child and family welfare are little different from pronatalist policy, except that the demographic rhetoric is lacking and with few exceptions (e.g., France) there are no special benefits for higher-order children. Measures include cash transfers and tax relief for parents, priority to families with children for subsidized housing, paid parental leave, and subsidized child care. The effects these policies have on birth rates are not easily demonstrated, but in Northwestern European countries, where they are best developed, both female workforce participation and birth rates are relatively high, at least in comparison to countries where such policies are absent, as in the more "familist" Southern Europe and East Asia. Central, Southern, and Eastern European and East Asian countries face the prospect of the sharpest population declines.
In the latter part of the twentieth century, European countries had tended to adopt restrictive immigration policies. But by the end of the century, European political and media opinion tended to see immigration as salvation from population decline and population aging. The notion that immigration can solve population aging can quickly be dismissed: preservation of current support ratios–that is, the ratio between persons of labor force age and persons of retirement age–would require very high levels of immigration, generating wholly infeasible rates of population growth. In the case of the Republic of Korea, according to a United Nations calculation, that country would require 6.2 billion immigrants (equaling the world's population as of 2002) by 2050. Future population decline could be averted by more modest, but substantial and fluctuating, levels of immigration: an average of 324,000 persons per year to Germany and 312,000 to Japan, a total inflow of some 16 or 17 million each by 2050. In the end, however, immigration cannot substitute for reduced birth rates. Any population trying to maintain its numbers by importing people to compensate for below-replacement fertility would eventually be replaced by the new immigrants.
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