Birth month,school graduation,and the timing of births and marriages

We investigated the timing of fertility and marriage in Sweden using exogenous variation in the age at school graduation that results from differences in birth month. Our analysis found that the difference of 11 months in the age at leaving school between women who were born in two consecutive months, December and January, implies a delay in the age at first birth of 4.9 months. This effect of delayed graduation also persists for the timing of second births and first marriages, but it does not affect completed fertility or the overall probability of marriage before age 45. These results suggest the existence of a relatively rigid sequencing of demographic events in early adulthood, and the age at graduation from school emerges as an important factor in determining the timing--but not the quantum--of familyformation. In addition, these effects point to a potentially important influence of social age, defined by an individual's school cohort, instead of biological age. The relevance of social age is likely due to social interactions and peer-group influences exerted by individuals who are in the same school cohort but are not necessarily of the same age.     

Seasonal Patterns of Reproduction in Matlab,Bangladesh

In Bangladesh twice as many births occur in December as in July. This paper examines the seasonal patterns of the risks of conception, fetal loss and return of menses post partum in a longitudinal study of 2,300 women in 14 villages of Matlab, Bangladesh. Life tables were estimated for each month of entry event and then ‘period’ life tables were constructed with the risks for a given calendar month. Confirming the results of earlier studies, risks of resumption of menses were higher in November and December, regardless of time elapsed since the last birth. Similarly, there are increased conception risks in the period from February to April for all fecundable women. The time of lowest fetal loss and stillbirth risks is in the cool season, though this variation makes only a minor contribution to the overall seasonality of births. The pattern of fecundability estimated from data on coital frequency did not match the pattern estimated from reported conceptions; these discrepancies imply possible seasonal changes in other parameters of fecundability besides intercourse.     

The data and the dynamics of the Chinese populations

Historical demographic data on populations of the Chinese cultural area including counts, registrations, and continuous records are discussed in terms of problems of analysis. For many decades, censuses, investigations, and registration reports yielded generally faulty data on the numbers, and the age and sex structures of the populations. The problem here is not the adjustment of age and sex structures, but the use of faulty structures to estimate the dynamics of the population in the absence of either successive investigations or vital statistics. This paper analyzes these problems according to historical eras (Chinese Farm Population 1919-1932) or geographical areas (Taiwan, Manchuria, etc.). The writer concludes that further pursuit of estimates that agree with the Chinese demographic realities of the period requires a) a wider integration of comparable data and b) adjustment of age structures in relation to the habitual errors in response, the systematic biases in registration, and the deviations reflecting erratic factors or historic events.     

Arima models of seasonal variation in U. S. birth and death rates

This paper applies methods of seasonal ARIMA time series analysis to U. S. monthly birth and death rates for January 1950–December 1978. For model selection, the conventional Box-Jenkins (1970, 1976) diagnostic checks are used in conjunction with some suggestions of Nerlove et al. (1979). This results in final models that contain significant second-order autoregressive components, as well as seasonal moving-average components, for both series. In addition, some evidence is found in the birth rate series for weekly periodicities. These findings imply the existence of a seasonal adjustment procedure that improves on the Census X-l1 program currently used by vital statistics agencies.     

Recent Trends in the Timing of First Births in the United States

We use vital registration data published since 1979 to update trends in the timing of first births. Two important trends are documented. First, the likelihood that childless women over age 30 will have a first birth has increased since the 1970s. This change shows that women born in the 1950s are "catching up" on fertility postponed at younger ages. Second, racial differences in the timing of first births are very large. For those born in the 1950s, nonwhites have first births much earlier, and far fewer nonwhite than white women will remain permanently childless. In the second part of the paper, we use these data for recent years to assess earlier projections of childlessness based on cohort and period approaches. We also assess the accuracy of stated intentions to have no children.     

Prospective study of birth interval dynamics in rural Bangladesh

Abstract A group of 209 married, fecund women in rural Bangladesh were studied prospectively for 24 months from 1969 to 1971 to define some of the biological and sociological factors relating to fertility performance. These women were selected from a larger study population of 112,000 that had been followed with a daily house-to-house vital registration programme since 1966. The selected women were interviewed bi-weekly and were asked questions about menstruation, pregnancy, lactation, husband's occupational absences, and monthly urine tests for pregnancy were taken. The results for 193 non-contracepting women revealed that the seasonal pattern of births previously observed in this population could be associated with a corresponding seasonal pattern of conceptions and that this was due to a seasonal trend in fecundability. The highest conception rates were in the coolest months of the year. Post-partum lactational amenorrhoea was very prolonged, averaging 17 months for women with a surviving child. The appearance of the first post-partum menstrual flow (onset of ovulation) also had a seasonal trend which could not be adequately explained. The median waiting time to conception, once menstruation had resumed was eight months. This interval was influenced by seasonal fluctuations, as well as by the age of women and by husbands' absences. The foetal wastage rate was 15·0 per 100 conceptions, with 62 per cent of the foetal losses occurring during the second month of gestation. Overall, the average birth interval was 33 months, with the prolonged lactational amenorrhoea accounting for almost 45 per cent of this interval. From the Department of Population Dynamics, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205.     

Revising Infant Mortality Rates for the Early Twentieth Century United States

Accurate vital statistics are required to understand the evolution of racial disparities in infant health and the causes of rapid secular decline in infant mortality during the early twentieth century. Unfortunately, U.S. infant mortality rates prior to 1950 suffer from an upward bias stemming from a severe underregistration of births. At one extreme, African American births in southern states went unregistered at the rate of 15 % to 25 %. In this study, we construct improved estimates of births and infant mortality in the United States for 1915–1940 using recently released complete count decennial census microdata combined with the counts of infant deaths from published sources. We check the veracity of our estimates with a major birth registration study completed in conjunction with the 1940 decennial census and find that the largest adjustments occur in states with less-complete birth registration systems. An additional advantage of our census-based estimation method is the extension backward of the birth and infant mortality series for years prior to published estimates of registered births, enabling previously impossible comparisons and estimations. Finally, we show that underregistration can bias effect estimates even in a panel setting with specifications that include location fixed effects and place-specific linear time trends.     

The Soviet Union: population trends and dilemmas

Focus in this discussion of population trends and dilemmas in the Soviet Union is on demographic problems, data limitations, early population growth, geography and resources, the 15 republics of the Soviet Union and nationalities, agriculture and the economy, population growth over the 1950-1980 period (national trend, regional differences); age and sex composition of the population, fertility trends, nationality differentials in fertility, the reasons for fertility differentials (child care, divorce, abortion and contraception, illegitimacy), labor shortages and military personnel, mortality (mortality trends, life expectancy), reasons for mortality increases, urbanization and emigration, and future population prospects and projections. For mid-1982 the population of the Soviet Union was estimated at 270 million. The country's current rate of natural increase (births minus deaths) is about 0.8% a year, higher than current rates of natural increase in the U.S. (0.7%) and in developed countries as a whole (0.6%). Net immigration plays no part in Soviet population growth, but emigration was noticeable in some years during the 1970s, while remaining insignificant relative to total population size. National population growth has dropped by more than half in the last 2 decades, from 1.8% a year in the 1950s to 0.8% in 1980-1981, due mostly to declining fertility. The national fertility decline masks sharp differences among the 15 republics and even more so among the some 125 nationalities. In 1980, the Russian Republic had an estimated fertility rate of 1.9 births/woman, and the rate was just 2.0 in the other 2 Slavic republics, the Ukraine and Belorussia. In the Central Asian republics the rates ranged up to 5.8. Although the Russians will no doubt continue to be the dominant nationality, low fertility and a relatively higher death rate will reduce their share of the total population by less than half by the end of the century. Soviet leaders have launched a pronatalist policy which they hope will lead to an increase in fertility, at least among the dominant Slavic groups of the multinational country. More than 9 billion rubles (U.S. $12.2 billion) is to be spent over the next 5 years to implement measures aimed at increasing state aid to families with children, to be carried out step by step in different regions of the country. It is this writer's opinion that overall fertility is not likely to increase markedly despite the recent efforts of the central authorities, and the Russian share of the total population will probably continue to drop while that of Central Asian Muslim peoples increases.     

Prospective study of birth interval dynamics in rural Bangladesh

A group of 209 married, fecund women in rural Bangladesh were studied prospectively for 24 months from 1969 to 1971 to define some of the biological and sociological factors relating to fertility performance. These women were selected from a larger study population of 112,000 that had been followed with a daily house-to-house vital registration programme since 1966. The selected women were interviewed bi-weekly and were asked questions about menstruation, pregnancy, lactation, husband's occupational absences, and monthly urine tests for pregnancy were taken. The results for 193 non-contracepting women revealed that the seasonal pattern of births previously observed in this population could be associated with a corresponding seasonal pattern of conceptions and that this was due to a seasonal trend in fecundability. The highest conception rates were in the coolest months of the year. Post-partum lactational amenorrhoea was very prolonged, averaging 17 months for women with a surviving child. The appearance of the first post-partum menstrual flow (onset of ovulation) also had a seasonal trend which could not be adequately explained. The median waiting time to conception, once menstruation had resumed was eight months. This interval was influenced by seasonal fluctuations, as well as by the age of women and by husbands' absences. The foetal wastage rate was 15·0 per 100 conceptions, with 62 per cent of the foetal losses occurring during the second month of gestation. Overall, the average birth interval was 33 months, with the prolonged lactational amenorrhoea accounting for almost 45 per cent of this interval.      

The Centenarian Question: Old-Age Mortality in the Soviet Union, 1897 to 1970

There is a long history of claims of extraordinary longevity among the populations of the Soviet Union, and the Russian Empire before it, especially in the Caucasus region. Exceptionally high proportions of centenarians have been reported in the censuses, and much publicity has accompanied the announcements of ‘super-centenarians’ living well beyond 150 years. The major question regarding this phenomenon of supposed extraordinary longevity is whether the claims are, indeed, true or, rather, the result of age exaggeration. This paper examines the available Russian and Soviet census and mortality data from 1897 to 1970 in order to assess Soviet claims of extraordinary numbers of centenarians. A detailed analysis of age overstatement in the census data and death registration statistics shows that the long history of longevity claims goes hand in hand with a long history of age overstatement. The extraordinary longevity observed in the Soviet Union is in all likelihood the result of that age overstatement.     

The effects of temperature on human fertility

Monthly birth and temperature data for a variety of states and countries are used to estimate the effect of short-run temperature fluctuations on fertility. Regressions of monthly births on a flexible specification of lagged monthly temperature show that temperature has quantitatively important effects on both seasonal and nonseasonal variation in births. Summer temperature extremes reduce conceptions in the southern United States, explaining a substantial part of the observed seasonal birth pattern. Extreme cold shows no evidence of affecting conceptions. The results also show significant seasonality in births even after accounting for temperature. Controls for monthly temperature do not explain the persistent spring peak in births in northern Europe. This finding suggests that other factors play an important role.     

Estimates of vital rates for the Canadian Indians, 1960–1970

The present paper is an attempt to evaluate the registered data on Canadian Indians collected by the Department of Indian Affairs and Northern Development and to prepare vital rates for 1960–1970 using the adjusted data. A cursory examination of registered data for the purpose of developing various demographic indices and for making future estimates of population indicates certain anomalies that call for a careful appraisal of the data. The main problem is the inconsistency in the reporting of births, due largely to the late registration of births. One plausible reason for late registration may be the increased outward movement of Indians from their reserves. Indirect methods are used to adjust the number of births and infant deaths reported annually since 1960. On the basis of the adjusted data, vital rates for the Canadian Indians are calculated for the period 1960–1970. The crude death rate decreased from 10.9 in 1960 to 7.5 in 1970. The infant mortality rate registered a drastic decline, from 81.5 deaths per 1,000 births in 1960 to 34.9 in 1970. During this same time period the birth rate also declined, from 46.5 to 37.2.     

Sample registration in India

India's ad hoc sample registration scheme for obtaining current estimates of rural birth and death rates for the whole country is being implemented quite rapidly. Five states have 140 sample units, and eleven states will have from 20 to 100 units in the study depending upon the stage of implementation by March, 1967.Essential elements of the project for each unit are: (1) continuous registration of vital events by a paid part-time local enumerator, (2) a six-month household survey to detect births and deaths which occurred during the previous six months, and (3) matching events from registration and surveys and field recheck of unmatched events to obtain the "best" count of real number of events. Preliminary results in a non-random sample indicate that the crude birth and death rates are around 37.1 and 15.7 per 1,000, respectively, for India's rural population, but these probably will be found to be on the low side.Most of the problems of implementation are operational or administrative rather than statistical: (1) For various reasons, some states are slow in agreeing to assume financial and other responsibilities for the scheme. (2) In many states, even after the scheme has been accepted, there are delays in recruiting the staff, training, and so forth. (3) The most serious problem in the whole project is maintaining control of field operations well enough at each stage to insure that prescribed instructions and methodology are being followed.Experience in India indicates that staged implementation of such projects is highly desirable when trained staff are limited. There still are a number of methodological problems which must be tested as the sample registration evolves. Sample registration is one of the first steps in the Indian program to. develop an adequate vital statistics system. Exploratory studies to measure completeness of civil registration are being done now in an effort to develop means of using civil registration data alone for measurement of vital rates.     

The seasonality of conception

Individual data on menstrual cycles of noncontracepting women living in Western countries were used in order to verify whether the biological seasonality of conception persists after sexual behavior is controlled for. Episodes of intercourse were recorded daily, and the time of ovulation was detected by a marker We find that the seasonality of conception changes with woman's age and frequency of episodes of sexual intercourse. In particular; for women aged 27-31 having only one act of intercourse during the six most fertile days of the menstrual cycle, the seasonality of fecundability is stronger In this age group in the Northern Hemisphere, if seasonality of acts of sexual intercourse is controlled, the monthly distribution of probability of conception is bimodal, with two maxima (September and January) and two minima (December and March). When unobserved characteristics of the couples are considered, this seasonal pattern of conception persists.     

Reconstruction of fertility trends for the female population of the U.S.S.R

Abstract The article describes fertility trends among Soviet women during the past 40 years as compared to American women during the same period of time. Period-specific fertility rates were arrived at by relating the annual total of live births to a pattern of age-specific fertility rates estimated for each year and also to the number of women for each single year of age. These rates were then appropriately re-arranged and compressed into five-year age groups to form a series of cohort-specific fertility rates. The findings rest on somewhat conjectural estimates of live births and numbers of women in the U.S.S.R., some of which were originally prepared before the 1959 Soviet census. The tentative evidence shows that changes in the period-specific fertility of Soviet women were far more irregular and dramatic in the past, than among American women. After World War II these rates dropped in the U.S.S.R. below those of the United States, except for women over 30 years of age. On the other hand, the cohort-specific rates of Soviet women, although declining from one cohort to the next, at present show their magnitude in the cumulative series for older ages to be marked by higher than among American women. This experimental investigation of fertility in the Soviet Union makes no claim to high standards of accuracy and validity. Its intended purpose is to stress the desirability of shifting emphasis from the temporal and prognostic type of study, characteristic of present-day demographic research about the U.S.S.R., to the generational and historical approach.     

Development of birth registration and birth statistics in the United States

The registration of vital events in the United States has always been under the authority of State and local areas. The preparation of national birth statistics has been made possible through a co-operative working arrangement between the Federal Government and the States. This paper traces the development of registration systems in the United States from colonial days to the present period. The absence of adequate registration systems throughout the country, during the nineteenth century, led to the use of data collected in the decennial population censuses of 1850–1900 for estimating birth rates. This procedure was abandoned because of the unreliability of the results. Steps leading to the formation of the national birth-registration area in 1915, when it included ten States and the District of Columbia, and. activities resulting in its completion in 1933 are discussed.

A major portion of the paper outlines the nation-wide test of birth-registration completeness conducted in 1940 in conjunction with the decennial census of population. Important results of the test are presented, and the methodology is explained. A similar test is being carried out in 1950. Data derived will be used to focus attention on local areas requiring registration promotion. Correction factors for statistical series based on registered events will also be obtained. The final section of the paper indicates the steps States are taking to improve quality of reporting on the birth record. Changes in the content of the standard certificate of live birth since 1915 are summarized and the statistics tabulated from birth certificates detailed.     

China's rural population statistics at the local level

Written for those who use Chinese population data and want a better understanding of their provenance and reliability and those who may directly utilize local level materials in studies of Chinese population and social structure, this report describes the statistical system of 1 rural county, Shifang Xian in the Chengdu Plain of Sichuan Province. It is based on interviews with local government officials, on examinations of population records and reports at different levels of administration, and on a sample survey of households conducted in the winter and spring of 1981. Until the mid 1970s, the primary source of China's rural population data was the household and vital events registers established in the 1950s. Following the formation of the Birth Planning Office in 1971, a separate reporting system of population statistics began to develop alongside the household registration system. The birth planning system uses the reports of team, brigade, and commune level cadres concerned with health work and women's affairs to provide a richer and more current set of vital events and birth planning data than the household registration system could provide. Discrepancies in data emerging from the 3 sources are bound to occur because of error and because of the different methods used in the compilation of data. Currently, there are 2 basic sources for population data in Shifang Xian: the monthly reports of the brigade level birth planning workers and the year end reports of the team accountants. The household and vital events registers, once central to population statistics, retain their legal role but have diminished importance for statistical purposes. There continues to be important questions about the operation of the statistical system. With increasing reliance on the newly developed birth planning statistical system for information on vital rates, Shifang has apparently moved from statistics based on date of registration derived from a de jure system of vital events registration to statistics based on date of occurrence derived from de facto or quasi de facto records of health workers and team accountants. As the latter system is more accurate, it seems likely that transition has been marked by discontinuities in time series of population counts and vital rates. The statistical system observed in Shifang is administered by highly motivated cadres. It apparently produces statistics of good quality. Linkage to the economy, constant updating, surveillance of pregnancy, and a level of overlap give the overall system considerable strength and should not produce substantial errors under normal circumstances. A serious remaining problem, i.e., the underreporting of infant deaths, is primarily due to inadequate training of statistical workers. Shifang Xian is an unusual county, and no conclusions should be drawn about the accuracy of rural population statistics based on performance there.     

Age at marriage and timing of the first birth

Summary An attempt has been made to measure the effect of age at marriage of brides on the timing of the first birth. In Australian vital statistics, first nuptial confinements have been tabulated by age of mothers and by single years of marriage duration in single months for the first two years and by single years for all other durations since 1916. A simple technique has been used to link such data with marriage cohorts. The study briefly reviews the prevailing patterns of the timing of first births by mothers' age at marriage and changes in this pattern since the marriages of the 1925/9 period. The analysis shows that after a period of relative stability of family formation patterns in the 1950s and early 1960s, women married in the late 1960s started postponing the first birth beyond the first two years of marriage. It is suggested that a fraction of the decline in total births recorded in Australia since 1972 can be attributed to the postponement of first nuptial confinements by women married in the late 1960s and early 1970s.     

The Level and Age Pattern of Mortality in Bandafassi (Eastern Senegal): Results From a Small-Scale and Intensive Multi-Round Survey

The data collected in the Bandafassi demographic study in Eastern Senegal, a small-scale intensive and experimental follow-up survey of a population of about 7,000 in 1983, were analysed to derive an estimated life table. The use of multi-round surveys, combined with anthropological methods to estimate ages and collect genealogies, has resulted in unusually reliable data. Taking into account the uncertainty of the estimates due to the small size of the population, mortality was high, with life-expectancy at birth close to 31 years; a pattern of infant and child mortality close to that observed in other rural areas of Senegal, with a very high level or mortality between ages six months and three years; a seasonal pattern in child mortality with two high-risk periods, the rainy season and the end of the dry season; an adult mortality pattern similar to that described in model life tables for developed countries; no significant difference by sex or ethnic group. The Bandafassi population study and a few similar studies suggest that one possible way to improve demographic estimates in countries where vital registration systems are defective would be to set up a sample of population laboratories where intensive methods of data collection would continue for extended periods.     

Changes in fertility in Japan by region: 1920–1965

Changes in fertility for the 46 prefectures of Japan are traced from 1920 to 1965, using census and vital statistics. During the period, substantial declines were recorded in both marital-fertility levels and the proportions of women of childbearing age who were married. Regional variation is pronounced in the timing of the onset of the decline in marital fertility. Only in the most industrialized districts did marital fertility begin to fall before 1950; thereafter, sharp declines were recorded in all parts of Japan. The marriage proportion, in contrast, was falling rather steadily throughout the islands between 1920 and 1950, after which the proportion stabilized. The decline in overall fertility that occurred before 1950was caused, then, primarily by a reduction in the proportion married; only after 1950 did a decline in marital fertility become a. major factor. The time pattern of change in marital-fertility levels and proportions married for Japan differs from that observed in western Europe, where low proportions married are recorded in the earliest national censuses. Apparently a fall in proportions married in western Europe preceded by one or two centuries the major sustained declines in marital fertility that were part of the so-called demographic transition.