Five decades of missing females in China.

This paper seeks to explain the dearth of females in the population of China in cohorts born from the late 1930s to the present. We demonstrate that in virtually all cohorts, the shortage of females in comparison with males is revealed when the cohort is first enumerated in a census. Subsequently it barely changes, an indication that female losses occur very early in life. Using the high-quality data from the censuses and fertility surveys in China, we show that many of the births of the girls missing in the censuses were not reported in the surveys because they died very young. The incidence of excess early female mortality (probably infanticide) declined precipitously in the Communist period, but not to zero. The recent escalation in the proportion of young females missing in China has been caused largely by rapidly escalating sex-selective abortion.

Age of entry into marriage and the date of the initiation of voluntary birth control.

It is widely known that modern economic development has been accompanied by the initiation and spread of effective limitation of fertility, and that generally the populations which experienced development at a late date also had a belated reduction in childbearing. Here a surprising relation is found between (and within) broad regions: the areas in which traditional age of entry into marriage was late were the areas in which marital fertility was reduced first.

The effect of age misreporting in China on the calculation of mortality rates at very high ages.

When mortality rates by age are calculated from recorded deaths and enumerated populations, rates at higher ages are typically in error because of misstated ages. Mortality rates for China in 1981 have been calculated from the number of deaths in 1981 in each household recorded in the 1982 census, and from the census population back-projected one year. Because age was determined from date of birth, and because persons of the Chinese culture have very precise knowledge of date of birth, the mortality rates even at high ages should be unusually accurate. This expectation is fulfilled for most of China, but severe misreporting of age is found in a province that contains a large minority of a non-Han nationality, which lacks precise knowledge of date of birth. Although the province contains only 1.3% of China's population, male death rates above age 90 for all of China are distorted seriously by the erroneous data from this location.

Recent trends in fertility and nuptiality in china.

The State Family Planning Commission of China has conducted two large-scale fertility surveys, in 1982 and 1988, covering sample households containing 1 million and 2 million persons, respectively. These surveys obtained lifetime histories, including age at first marriage and at each birth for female members of the households from ages 15 to 67 in the first survey and from 15 to 57 in the second. The data provide detailed information on the extraordinary decline in the rate of childbearing in China (by 60% from 1970 to 1980). Because rising age at marriage played a significant role in this decline, the effect of changes in the pattern of entry into marriage on childbearing since 1980 was examined. There was a sharp increase in overall fertility (the total fertility rate) from 1980 to 1982; after falling to slightly below the 1980 level in 1985, the rate rose in 1985 and 1986 to well above that of 1980. A major factor in this arrested and partially reversed decline was a boom in marriage that followed a relaxation in 1980 of locally administered restrictions on marriage before the officially designated desirable age. In fact, the total fertility rate of married women (summed over duration of marriage rather than age) averaged much lower in the mid-1980s than in 1980. The summary rate of bearing second children increased markedly in the 1980s when calculated by age of women, but declined when calculated by duration of marriage, given the inflated number of recently married women.

Some relations among cultural traditions, nuptiality and fertility.

PIP: Demographic transition is a period characterized by changes in mortality and fertility that accompany modernization and economic development. Typical features of age at first marriage among populations in different stages of demographic transition are described including the changes in age at marriage, the association between marriage age changes and fertility control, and the role of cultural and traditional behavior in influencing age at marriage and initiation of fertility control. In the Western model, there was a late age of marriage for women between 23 and 28 years old, and a high proportion of women who remain single until 50 years old (10-25%). The Eastern European model was one of moderately early marriage (mean age 19-22) and a small proportion remaining single (2-5%). The third model was Asian and African with early (mean age of 18 years) and universal marriage (1% unmarried). The reduction in number married was associated with reduced fertility. The differences between the Eastern and Western models were in household composition. In premodern societies, any fertility control present was governed by custom and limited biomedical influences such as duration of breast feeding and sexual abstention following a birth. These practices were not considered deliberate fertility control. The mean age of marriage in India was 14 years until 1941 and slowly reached 18.4 years in 1981. Fertility did not begin to decline until after 1960. Examples are given of the close association between marital fertility that is voluntary controlled and mean age at marriage. The influences of culture and traditions on the association between mean age of marriage and voluntary fertility control are shown by examples from the Soviet Union. The eastern part of the Soviet Union experienced a rise in mean age of marriage and an unsustained decline in marital fertility similar to that in China. There were also similarities in nuptiality and fertility between other areas in the Soviet Union and neighboring populations in Eastern Europe. Examples of the influence on culture are given for China, Taiwan, Korean, India and Bangladesh.^ieng

Age patterns of mortality for older women: an analysis using the age-specific rate of mortality change with age.

"In this paper we propose a mortality measure that seems useful in analyzing age patterns of death rates. The measure, which will be denoted by k(x), indicates the proportional increase or decrease with age in the risk of death at a given age x, and is called the age-specific rate of mortality change with age." Estimations are presented for women in 10 countries. "Eight of the selected sets of data are for developed nations in the 1960s and 1970s, and the other two sets of data, for Taiwan, 1931-35, and for Germany, 1910-11, represent relatively high mortality. For France and West Germany, three different periods are included for an investigation of cohort effects on the observed age patterns." Other mathematical models of age-specific mortality rates are discussed and compared. (SUMMARY IN FRE)

Estimation of the number of persons at advanced ages from the number of deaths at each age in the given year and adjacent years.

"In this article the rate of increase of the population at each age is estimated from the rate of increase in the number of deaths, and in this way a close approximation of the number of older persons at each age is derived from the accurately recorded number of deaths in three consecutive years centered on the year in question. The method is illustrated by applying it to Sweden, England and Wales, and Italy." (SUMMARY IN FRE AND ITA)

Demographic effects of scientific progress.

PIP: This essay refutes the commonly held view that the demographic transition in the west occurred as a result of scientific progress, but admits that the drop in mortality in the developing world since 1950 is largely due to technology. Human populations have grown at about 0.05% annually for 10,000 years, until about 1750, when the rate grew to 0.5%, then to 0.7% after 1900, and to 2% in the 1960s. Looking at life expectancy, which was about 35 years in the 18th century and 40 in the 19th in Europe, as well as advances in treatment and prevention of the major killer diseases, it is apparent that death rates fell substantially well before any effective therapy or immunization was developed. This can be demonstrated for tuberculosis and smallpox. Probably, life-style changes such as wearing washable cotton clothing, bathing, and better nutrition contributed to longer life. Advances in the understanding of contagion and infection contributed toward eradication of typhoid and cholera after 1850. Hence, public health projects such as sewage and water systems, better housing and working conditions, helped stop typhoid and diarrhea and to prolong life generally. The decline in fertility documented in the west also took place before any scientific birth control methods were available: only folk methods such as withdrawal, and social methods such as later marriage were responsible. In the less developed world, death rates began to plummet after 1950, largely due to immunization, mosquito control and other advances in health technology. It is hoped that contraceptive technology, with methods unrelated to sexual behavior, will reduce births in parallel. In conclusion, although science may not have been responsible in detail for the demographic transition in the west, scientific ideas prompted new attitudes about social change and secularism, which may have played a role in lowering birth rates.^ieng

Calculation of age-specific fertility schedules from tabulations of parity in two censuses.

The mathematics of stable populations recently has been generalized to cover populations with time-varying fertility and mortality by a modification incorporating the sum of age-varying growth rates in place of the fixed growth rate of a stable population. Equations that characterize nonstable populations apply to any cohort-like phenomenon with a measurable property that cumulates gains or losses through time. In particular, the equations fit the relation between a population's average parity at a given age and age-specific fertility rates previously experienced at lower ages. Techniques devised to derive an intercensal life table from single-year age distributions in two censuses are adapted to estimate accurate intercensal fertility schedules from distributions of parity by age of woman in two censuses. Birth-order specific fertility schedules are also estimated.

An extension and simplification of a new synthesis of age structure and growth.

PIP: This article is an extension of an article by Samuel H. Preston and Ansley J. Coale in which a set of general relations that apply to any population was formulated.^ieng

A reply to Kim's comment.

PIP: This reply criticizes Kim's note as incorrectly characterizing the essential feature of the method proposed for life table construction. The method suggested for estimating N(a), the number attaining age 2 during the intercensal period, is to make a separate estimate of the contribution to N (a) made by each single-year cohort that attains 'a' during the period between censuses. Each cohort estimate is constructed by interpolation, utilizing as data the recorded number in the relevant single-year cohorts in the 2 censuses. 2 methods of interpolation were proposed. 1 is an iterative procedure that constructs a preliminary life table by linear interpolation for each cohort and then derives more refined interpolation factors from this preliminary life table. The other procedure derives interpolation factors on the assumption that the proportionate distribution of deaths by age as each cohort moves from the earlier to the later census date is the same as the proportionate distribution of deaths by age over the same age range in a model life table. The advantage of the proposed procedure is that it supplies better estimates of N (a) than do alternative methods. The author concedes that a life table calculated from accurately recorded deaths and an accurately enumerated population would ordinarily be superior. However, he also notes that in the absence of registered deaths data, there is no precise enough conventional method to yield accurate values of average intercensal single-year age-specific mortality rates from nothing more than 2 accurate censuses 11 years apart. A common procedure for calculating life expectation at a very advanced age is to calculate the reciprocal of the death rate among persons over the age in question.^ieng

Life table construction on the basis of two enumerations of a closed population.

The author demonstrates that an accurate detailed life table that represents average mortality experience between two censuses can be constructed if the censuses provide accurate records of the single-year age distribution of a closed population. This life table can begin at age zero if accurate data on the annual number of births during the inter-censal period are available; otherwise the first age in the life table must equal the duration of time between the censuses. "The estimation technique involves the calculation of the number of persons attaining each age during the period between the censuses and the determination of the average rate of increase in the number at each individual age. The success of the technique comes from the use of interpolation to calculate how many in each cohort attain each exact age the cohort passes through between the censuses." The estimation technique is tested using two alternative methods of interpolation. Some illustrations based on data for Sweden and China are included.

Estimation of expectation of life at advanced ages.

Comments are presented on a formula developed by Enzo Lombardo "for the relation between the death rate above age a and the growth rate above age a (where a is an advanced age, above 55 or 60) on the one hand, and the expectation of life at age a on the other." Estimates obtained by this method are compared with results obtained by the method of S. Horiuchi and A. J. Coale. It is concluded that "the formula proposed by Horiuchi and [Coale] produces much more accurate estimates, with a maximum error of 0.03 years." The author describes a way in which Lombardo's method "can be modified to give estimates of precision comparable to the Horiuchi and Coale estimates." (summary in FRE, ITA)

The demographic transition.

Demographic transition is a set of changes in reproductive behavior that are experienced as a society is transformed from a traditional pre-industrial state to a highly developed, modernized structure. The transformation is the substitution of slow growth achieved with low fertility and mortality for slow growth maintained with relatively high fertility and mortality rates. Contrary to early descriptions of the transition, fertility in pre-modern societies was well below the maximum that might be attained. However, it was kept at moderate levels by customs (such as late marriage or prolonged breastfeeding) not related to the number of children already born. Fertility has been reduced during the demographic transition by the adoption of contraception as a deliberate means of avoiding additional births. An extensive study of the transition in Europe shows the absence of a simple link of fertility with education, proportion urban, infant mortality and other aspects of development. It also suggests the importance of such cultural factors as common customs associated with a common language, and the strength of religious traditions. Sufficient modernization nevertheless seems always to bring the transition to low fertility and mortality.

Recent trends in fertility in less developed countries.

The rate of increase of population in less developed countries accelerated rapidly from 1850 to 1960 because of a rapid decline in mortality while fertility remained high. In the 1960's, the birth rate as a whole began to decline more rapidly than the death rate--very rapidly in some populations, most notably that of China, more gradually in others, and not at all in some of the poorest populations. The momentum of growth implies continued increase in populations for several decades even in countries where fertility has fallen the most, and very large additional increases where there has been no decline in the rate of childbearing.

Age structure, growth, attrition and accession: A new synthesis.

PIP: This paper shows that each equation describing relationships among demographic parameters in a stable population is a special case of a similar and equally simple equation that applies to any closed population and demonstrates some implications of these new equations for demographic theory and practice. Much of formal demography deals with functions that pertain to individuals passing through life, or to a stationary population in which births of individuals are evenly distributed over time. These functions include life expectancy, probabilities of survival, net and gross reproduction rates, expected years spent in various states and the probability that certain events will occur in the course of life. The stable population model permits the translation of population structure or processes in a more general type of population, with constant growth rates, back into equivalent populations for a stationary population. The method for translation developed in this paper, requiring only a set of age-specific growth rates is even more general, applying to any population. Age specific growth rates may also be useful for performing reverse translations, between a population's life table and its birth rate or its age distribution. Tables of numbers of females by single years of age in Sweden are used to illustrate applications. Tables summarize the basic relations among certain functions in a stationary population, a stable population and any population. Applications of new equations, particularly to demographic estimation of mortality, fertility and migration, from incomplete data, are described. Some other applications include; the 2 sex problem, increment decrement tables, convergence of population to its stable form, and cyclical changes in vital rates. Stable population models will continue to demonstrate long term implications of changes in mortality and fertility. However, in demographic estimation and measurement, new procedures will support most of those based on stable assumptions.^ieng

Duration-specific marital fertility in Egypt.

PIP: Because of the discovery of substantial underreporting of births, deaths, marriages, and divorces in Egypt, the original report of the Committee on Population and Demography on duration-secific fertility rates of married women in Egypt was modified by using estimated calculations of these vital statistics. The original report involved the calculation of duration-specific fertility rates of married women in Egypt by first estimating the number of currently married women at each duration (by single years of duration under duration 5, and by 5-year intervals of duration up to duration 20). The calculation required data on the annual number of marriages and on the number of divorces each year, classified by duration of marriage, and estimated of the number of deaths of married persons of each sex by duration of marriage. From these data, it is possible to estimate at each date the number of marriages still intact of those that took place 0-1, 1-2, 2-3, 3-4, 4-5, 5-10, 10-15, and 15-20 years earlier. Deficits in the recorded number of marriages cause implausible variations in duration-specific fertility. It is important to discover the extent to which the recent apparent increase in birthrate is genuine, and the extent to which it is the result of improved registration. Factors causing an increase in fertility could be increase in the fraction of the population of childbearing age that is currently married; reduction in the interbirth intervals in the early years of marriage as a result of shorter average period of breastfeeding; or reduction in the practice of contraception or in the effectiveness of such practice. Duration-specific fertility rates were recalculated for 1966-79 by estimating the number of currently married women at each duration of marriage. If registered data are accurate, there was a slight increase in marital fertility after 1975 or 1976, and a large increase in 1979. The sharp rise in 1979 should not be accepted without study of registration procedures. Underregistration of births in the early 1970s was estimated at 4%. Since births are recorded by year of registration rather than year of occurrence, improved registration might include not only a more complete record of current births, but also the backlog of previously unregistered events.^ieng

A reassessment of world population trends.

This reassessment is limited to observations concerning trends in mortality and fertility and concerning longrun prospects for population growth. Recorded changes in mortality are compared with 3 projections made many years ago. Projections of European mortality made in 1941-42 understated by a wide margin the actual increase in expectation of life because of unforeseen technological changes in the prevention and cure of fatal disease. On the other hand, a projection made in 1955 for India, foreseeing a rapid rise in the 1950s and slower progress later on because of the exhaustion of the easier gains, appears to have been accurate and also to depict the prospects in other populations of relatively high mortality and low income. A different projection of life expectancy in Mexico was also quite close to actual changes in Mexican mortality; it was based on a universal curve constructed to represent how life expectancy rises, increasing ever more slowly as it approaches an upper limit. This curve (1 for each sex), constructed for projection of Mexican mortality, is employed as a standard of comparison for mortality changes in many countries. A number have followed the standard for females very closely for more than 3 decades; in developed countries, male life expectancy has generally fallen short of the standard. The almost universal low fertility in developed countries contrasts with the great diversity of levels and trends of fertility in developing countries, some of which retain undiminished high fertility and others of which have recently attained rates of childbearing as low as in the developed areas. Instances of surprisingly little change and surprisingly rapid change in fertility are described. In the future, growth of populations of developed countries will probably be slight; the future rate of increase in the developing areas depends on the unpredictable timing and pace of childbearing reduction in populations where fertility remains high. In the long run, world population growth may resume its typical pattern of moderate growth interrupted by catastrophic setbacks.