the assumption of responsibility for the welfare of the world















Fertility is the general ability or tendency to produce offspring. We speak of high fertility in a given population when a representative woman is likely to have more children, and low fertility when she is likely to have fewer children. One measure of fertility is the total fertility rate, which is the total number of children an average woman will have. We can speak of the fertility rate of a place, or of a period of time, because fertility varies considerably with social, economic, and technological circumstances.

The birth rate is a measure of the frequency of births in a population, generally rendered as the annual number of births per thousand people. The death rate is comparable, again generally an annual rate per thousand. When the birth rate exceeds the death rate, we have a state of natural increase; the population is rising through reproduction alone, as opposed to something like immigration. When the death rate exceeds the birth rate, we have a state of natural decrease. And of course, when the birth and death rates are equal, we have population stability.

The replacement rate is the number of children a woman must have, on average, to produce one daughter who survives through childbearing years — in other words, to replace herself. In a perfect world, the replacement rate should be 2 — if every woman has two children, then randomly half of those children will be girls, the same as the number of women themselves, and they will all grow up to be potential mothers. In reality, the replacement rate is always slightly higher than 2 because boys are born more frequently. And only in a perfect world do all children live to reproductive age. That means that, in regions with high mortality (at all stages of life — infant, child, adult), the replacement rate can be higher than 3, as women must have well more than two children because the children are less likely to live through childbearing years.

Thus, when the total fertility rate equals the replacement rate, a society should have population stability. When fertility exceeds the replacement rate, there should be natural increase, and when it is below replacement rate, there should be natural decrease.

Life expectancy is simply the length of time a person is expected, at birth, to live. This is based on demographic average for a place and time. In the modern era, this number gets larger and larger, owing to advances in technology and health care. Obviously, some demographics have longer life expectancies than others; for instance, you would guess that rich people live longer than poor people. Life expectancy can also vary by gender, though; in the West, women live significantly longer. That is not universal; in India, life expectancy for men and women is the same.

According to the Demographic Transition Model, there are five stages of a society’s development. In Stage I, the birth rate (green) and death rate (red) are both high, and the population is stable. This accounts for nearly all of human existence. While the hunting-gathering period of the human species also accounts for nearly all of human existence, Stage I and the hunting-gathering period are not identical. Obviously, they occupy most of the same space, but Stage II doesn’t begin precisely with the advent of agriculture. In Stage II, the birth rate remains high, while the death rate falls. The fall in the death rate is the result of advancing technology — better nutrition, better health care, increased security. Stage III is the period where the birth rate remains high but stable, and the death rate remains low but stable. In Stage IV, the birth rate falls, while the death rate remains stable. As society changes more, the birth rate continues to fall, so that finally, in Stage V, the birth rate falls below the death rate. As the diagram shows, in Stages II-IV, the birth rate is higher than the death rate, meaning the society is experiencing natural increase. Stage V is a period of natural decrease.

The death rate falls earlier in development than the birth rate because cultural change lags technological change. The habits and values of earlier society persist even when they are no longer needed for society’s survival. In other words, people are conditioned to have a preference for large families, and it takes a long period and further changes for a new culture to develop.

The main driver of lower fertility is confidence in the health prospects of the child. Other factors correlate with low fertility, notably education, especially of women, and wealth, both of society as a whole, and of the individual household. The education of women leads to a better understanding of reproductive options, and it also leads to women working outside the home; both of these contribute to women having fewer children. Wealth naturally means better health care and technology; these keep children alive, but also correlate with women working outside the home.

The most important figure in the historical debate about population was Robert Malthus (1766-1834), who argued that population grows geometrically (exponentially), but the food supply grows arithmetically (linearly), so that eventually food supply limits population growth. Typically this would happen by famine, which simply means a widespread food shortage regardless of cause.

Population becomes an environmental issue through the question of overpopulation and the scarcity of resources. This idea was given a significant boost with the publication of ‘The population bomb’ (1968), by Paul and Anne Ehrlich (published under Paul’s name alone), which predicted a range of environmental and humanitarian disasters due to overpopulation (on a timetable which proved inaccurate). The Ehrlichs also called the US the world’s most overpopulated state, based on the concept of consumption overpopulation, which is essentially total consumption — the product of population size and consumption per capita. The US is one of the world’s most populous states, and, as an advanced industrial state, has a very high rate of consumption per capita.

Economic progress leads to low fertility, as people feel more secure in the future of each of their children and wish to provide better for each one. This has meant that native-born populations in prosperous societies have gotten progressively older, on average, as people live longer and fewer children are born in each succeeding generation. This disrupts the structure of the workforce, as there are, relatively, more retirees and fewer workers to support them. Retirees are not only not productive, but they often consume more, through their health-care needs. The United States is at an advantage relative to other advanced economies, because it has comparatively-high immigration. The immigrant population is not only younger, but has a higher birth rate. By contrast, low-immigration advanced economies like Japan are experiencing a serious imbalance, with too few young workers.

Concern about overpopulation has led to the same age imbalance as a result of deliberate government policy, namely the one-child policy of the People’s Republic of China, issued in 1978. In its basic form, the policy limited each affected couple to a single child. There have always been exceptions to the policy, and in later decades those exceptions were expanded; for example ethnic minorities were never affected, and most (but not all) couples who were both only children could have a second child. Nonetheless, the policy has applied to many Chinese and has been in place for decades, so has dramatically affected Chinese society. In addition to the imbalance in age, the long-standing Chinese preference for male children (hardly unique to China) has led to sex-specific abortions and to a further exemption for certain parents whose first child was a girl; both of these have meant significantly more boys than girls in affected generations, which means many boys have been unable to find partners in adulthood. The one-child policy has been a direct challenge to at least two elements of Chinese religious culture — ancestor worship and Confucianism. The living have an obligation to perform rites for dead ancestors, and children have numerous obligations to their parents, including supporting them in old age. Such support is a common obligation throughout the world, but unthinkable to violate in a Confucian society, and when one child is the sole support for two parents and possibly three or four grandparents, the burden is unusually high. The flip side of this is that only children are focuses of parental and grandparental attention, often spoiled (“little emperors”, as they have been called in China), but also subject to higher expectations as the sole representative of so many ancestral lines. In 2015, the PRC announced a transition to a new policy, in which all affected couples will be allowed to have two children instead.

A generation, in the original and precise sense, is a group of persons with a common ancestor and removed from that ancestor by the same number of intermediate ancestors — parent, grandparent, and so on. Thus, a person is in the same generation as her siblings, first cousins, second cousins, third cousins, and so on, regardless of their relative ages. The term ‘generation’ is also used for any heuristically-defined birth cohort within a society, to which various traits and behaviors are often then attributed. The living “generations” commonly identified in the US and other parts of the West (with their approximate first year of birth) are: Greatest Generation (1901), Silent Generation (1928), Baby Boom (1946), Generation X (1965), Millennials (1980), Generation Z (1997), and a final cohort with as yet no popular name beginning around 2013. The dates and even the names are not matters of universal agreement. The attributed traits and behaviors would be statistical generalizations even for precisely-defined cohorts. In other words, these “generations” serve much more as conventions than as technical classes.



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