A study of the correlation bias of unrecorded events by two independent enumeration systems

In this paper the allegation that, when using the Chandrasekar-Deming technique with two independent enumeration systems to record the incidence of vital events and migrations, each individual system misses the same type of event is investigated. If this correlation bias were to occur frequently enough, it could result in a serious underestimation of a given type of event. Using vital events and migrations data derived from a longitudinal survey conducted in Liberia between 1969 and 1973, the estimated number of recorded events is tabulated into homogeneous groups that are demonstrated to affect omission rates. The proportion of missed eyents is computed separately for each enumeration system, and the presence or absence of a significant correlation mathematically determined. The results of this study suggest that no significant correlation could be demonstrated in the type of birth, death or infant death that was commonly missed by each individual enumeration system. This indicates that the omission of a birth, death or infant death was apparently a random occurrence as far as the individual casefinding systems were concerned. The authors conclude that any underestimation of vital events from this type of correlation bias may not be as serious as originally imagined.

In contrast to this observation, the omission of particular types of migrations by each enumeration system was apparently not a random occurrence, but was associated with the direction of migration. This implies that selected migration rates in the liberian survey were probably understated and this could happen in other longitudinal surveys, unless specific precautions are taken to avoid it.     

Comment on “compromised birth outcomes and infant mortality among racial and ethnic groups”

Frisbie, Forbes, and Pullum (1996) show that it is meaningful to account for low birth weight, preterm delivery, and intrauterine growth-retardation when analyzing differences in compromised birth outcomes and infant mortality among racial and ethnic groups. I compare their findings for the 1987 U.S. birth cohort with findings for the 1988 U.S. birth cohort, using linked birth and infant death vital statistics from the National Center for Health Statistics. I focus on their calculation of fetal growth curves, which are highly at odds with the curves commonly used in the obstetric and pediatric literature. I compare birth outcome distributions and infant death probabilities using Frisbie et al. 's method and other standards. I conclude that Frisbie et al. 's method is not suited for the study of intrauterine growth-retardation at the population level because of the major flaws in gestational age measurement that exist in the type of data they use. An appropriate alternative is to apply a standard of normal intrauterine growth derived from antenatal estimation of fetal weight-for-gestational-age to the vital statistics data.     

A comparison of different survey techniques for obtaining vital data in A developing country

This article presents estimates of the sources and the extent of observation errors in different questionnaires and methods used to collect birth and death data in the 1961-63 multi-purpose sample survey of Morocco.The questionnaires used in the analysis of the three survey rounds were a list of household members (Rounds1 and 2) and a roll-call (Round3); retrospective death (Rounds1, 2, and 3) and birth (Round 3) queries; a date-of-birth tabulation (Round 2); and a household check-sheet to explain differences between Rounds 1 and 2. All available questionnaires for a given household were brought together and collated to provide several sources of information on births and deaths and a basis for assessing errors.From this analysis, the survey attempted to define the nature and to estimate the frequency of the errors which would have occurred if more restricted types of survey design had been used. Results, based on the period between Rounds 1 and 2, led to three major conclusions.First, if vital data had been collected with a single-round retrospective procedure, gross error (over enumeration plus underenumeration) would have been 17 percent for births and 36 percent for deaths. There is a net error of overenumeration of 3 percent for births (1.4 per1,000population) and 9 percent for deaths (2.3 per1,000population).Second, if two rounds were available to permit a combination of household composition follow-up and a retrospective mortality questionnaire, overenumeration would be almost entirely eliminated and underenumeration would be noticeably reduced. Third, most of the remaining errors of underestimation may be attributed to (1) an estimated number of infants born and deceased between two rounds and missed by all questionnaires, (2) matching failures caused by the absence of adults at Round 1, and (3) matching errors.     

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.     

The effect of child mortality experience on subsequent fertility: in Pakistan and Bangladesh

Summary This paper presents an empirical analysis of the effects, behavioural and biological, of child mortality experience on subsequent fertility in two South Asian Islamic nations. Data for the investigation came from retrospective pregnancy histories of 2,910 currently married women interviewed in the Pakistan National Impact Survey (1968-69) and from longitudinal vital registration data (1966-2070) of 5,236 women residing in a rural area of Bangladesh collected by the Cholera Research Laboratory. The aim of this study was to assess the importance of the child-replacement motivational response to child death experience after biological effects have been controlled adequately. A common approach employed previously has been to examine cumulative fertility according to child death experience. In Pakistan and Bangladesh, a consistently positive relationship was demonstrated between the number of children ever born and the number of child deaths. This method, however, did not exclude the inverse relationship, the influence of fertility on mortality, nor did it dissect out behavioural from biological effects. Utilizing a measure of subsequent fertility, live-birth-to-live-birth intervals, the study further illustrated another common pitfall. Since the risk of infant death, which leads to shorter birth intervals, is associated with the mother's reproductive history, women with child mortality experience are more likely to experience shorter intervals because of the biological effect of subsequent infant death. Behavioural influences may, therefore, be observed by considering only those birth intervals in which the first-born child survives to the end of the interval. With these limitations controlled, very few, if any, behavioural influences were noted in the Pakistan and Bangladesh data. Median birth intervals in Pakistan varied between 35-43 and 41-42 months, increasing with parity. Within each parity group, no consistent difference was observed between women with and without previous child loss. In Bangladesh, the median birth interval for all women with a surviving infant was 37-2 months. This was shortened to 24-31 months by an infant death. When intervals with infant deaths were excluded, little or no behavioural influence was detected among women of the same parity, but with varying levels of previous child loss. Even without behavioural effects, elimination of infant mortality in Bangladesh would reduce fertility by prolonging the average period of post-partum sterility. In the Bangladesh setting, however, the size of the effect was only about four per cent. This modest effect, more-over, was counterbalanced by an overall increase of net reproduction by seven per cent due to better survivorship of infants.     

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.     

New estimates of the vital rates of the United States black population during the nineteenth century

The difficulties of obtaining credible estimates of vital rates for the black population throughout the entire nineteenth century are overcome in this study. The methodology employed the notion of deviating networks of mortality rates for each general mortality level, which was taken from the United Nations studyThe Concept of a Stable Population. Period life tables and vital rates for intercensal periods were generated from the new estimates of the black population at each census date. The results of this study are highly compatible both with the life tables for the death-registration states in the twentieth century and the recent Coale and Rives reconstruction for the period from 1880 to 1970 and with several estimates of vital rates previously made for the mid-nineteenth century. This study places the mean life expectancy at birth for the black population during the nineteenth century at about 33.7 years for both sexes. The infant death rate (1000m (0)) is shown to have varied between 222 and 237 for females and between 266 and 278 for males. The intrinsic crude death rate centered on 30.4 per thousand during the century, while the birth rate declined from 53.2 early in the century to about 43.8 at the end.     

The Vital Statistics Method of Estimating Net Migration By Age Cohorts

The focus of this paper is the development and testing of a method of estimating deaths which occur during a decade to aging birth and death cohorts, so that it may be possible to estimate net migration by the vital statistics (VS) method for age cohorts. Until now the VS method has been used only in making estimates of total net migration.The results obtained by using the VS method for age cohorts show that (1) the average census survival rate (CSR) method generally yields algebraically lower estimates of net migration than does the VS method; but (2) there are some striking exceptions which are apparently associated with errors in census enumeration by age, sex, and color. Comparisons between the average CSR and the VS methods are shown, by age, for both the North Carolina and the coterminous United States populations.A cursory examination of these comparisons suggests that the exclusive use of the VS method in estimating net migration for age cohorts may lead to substantial error. Finally, the magnitude of these errors in estimating net migration, as well as in census enumeration, can be roughly approximated if it is assumed that the use of the CSR method yields reasonably accurate estimates of net migration.     

Sample registration in India

Abstract The Sample Registration Project in India is designed to obtain current estimates of birth and death rates for the whole country. It is being implemented quite rapidly. Rural and urban areas in all states and Union Territories in India will be covered before the close of 1969. Bigger states have 150 sample units in rural areas and 60 to 100 units in urban areas. Essential elements of the project for each unit are: (1) continuous enumeration of births and deaths in respect of usual resident population by a paid part-time local enumerator; (2) a six-month household survey to detect births and deaths which occurred to the usual resident population during the previous six months; and (3) manual matching of all event from enumeration and surveys and field re-check of unmatched events to obtain the 'best' count of real number of events. The results of a full-scale sample in four states and pilot sample in ten states indicate that the crude birth and death rates are around 40 and 18 per 1,000, respectively, for India's rural population. Most of the problems of implementation are operational or administrative rather than statistical. The main problem in the whole project is to maintain control of field operations well enough at each stage to ensure that prescribed instructions and methodology are being followed; particularly in the six-month survey. Experience in India indicates that sample registration techniques are capable of providing reliable birth and death rates in similar conditions in developing countries. However, there are still a number of methodological problems which must be tested as the sample registration evolves.     

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.     

从"五普"地市数据看生育政策对出生性别比和婴幼儿死亡率性别比的影响

以"五普"数据为基础,分析全国"地市"的出生性别比、婴儿死亡率性别比与生育政策的关系.本文的分析表明实行"第1个孩子为女孩,间隔几年允许生第2个孩子"生育政策的人口比例越高的地区,出生性别比和婴儿死亡性别比失常越严重;实行较为宽松生育政策的地区比较接近正常.实行较为宽松的生育政策有利于解决目前出生性别比严重失常和女婴死亡严重偏高的问题.     

Matching experimentation in a dual record system for births and deaths in Morocco

Summary In an effort to improve the quality and completeness of birth and death reporting in Morocco, a sample of 84,000 persons was established, for whom birth and death data were collected by two methods. Each household was contacted once a month by interviewers in a registration method; independently, each household was interviewed once every six months by a survey team. Interviewing continued from April 1972 to July 1973. Results of these two methods were then compared through matching the vital events recorded by the two sources. First a 'true match status' was established by teams of 'experts', supplemented by field verification of uncertain cases. Of the 15 variables on the vital event reporting forms, eight were studied to establish the optimal tolerance limits for deciding whether any two completed recording forms (one from each method) were recording a single birth (or death) or two different ones. Next, those characteristics were selected which introduced the fewest matching errors; for births, this was the dwelling unit number, the name of the mother, and the name of the baby; for deaths, the dwelling unit number, the name of the person, and the name of the head of household. Aside from its manifest function, the matching operation also improved the fieldwork and helped to clean the data.     

Estimation of vital rates for Ghana

Abstract A complete and efficient registration system, of the type which would provide good data on births and deaths, does not exist in Ghana. However, registration of vital events is supposed to be compulsory in 39 towns in the country but the data collected in these areas are too inadequate and defective to provide a sound basis for the analysis of the dynamics of population growth. The results of the censuses conducted by the colonial governments are so defective and unreliable that they do not allow scientific research in the field of population analysis. Before 1960, therefore, when the national census and the post-enumeration survey (based on a 5% sample of the population) were carried out, estimates of fertility and mortality levels were little more than guesses. In this study an attempt has been made to utilize the information on the age-sex composition provided by the 1960 census and post-enumeration survey data on births and deaths to determine, as far as possible, the levels of fertility and mortality and the rates of population growth in Ghana. The fertility estimates-i.e. a crude birth rate of 50, total fertility rate of 6.9 and a gross reproduction rate of 3.4-show that Ghana's fertility is one of the highest in the world. An expectation of life at birth of 40 years, an infant mortality of 160 and a crude death rate of 23 appear to be the most plausible estimates. These estimates yield a rate of natural increase of 2.7% and a growth rate of 3.0% per annum.     

Bias in Age at Marriage in Family Reconstitutions: Evidence from French-Canadian Data

Age-at-marriage estimates from family reconstitutions may be biased downward when they are based only on marriages of people who continue to live in their parish of birth, because when the probability of migrating rises with age, younger people are selected in preference to older ones. Micro-simulations show that the bias can have dramatic effects. In this paper French-Canadian data are used to investigate the importance of the bias and to verify empirically the micro-simulation results. Although a high proportion of people moved between birth and marriage, the bias had virtually no effect, given the specific characteristics of the migrations. If one cannot avoid discussing the timing of migration before marriage, when measuring age at first marriage using only data on “stayers”, it is just possible that in most settings, it is the same for those who lived in their parish of birth, and those who had moved.     

出生性别比失衡与社会政策的柔性调节

出生人口性别比失衡问题日趋严重．不进行治理将带来严重的社会后果。目前采取的一些治理人口出生性别比的措施。如加强宣传教育、加强计划生育管理等。这些手段在一定程度上能对人们的生育观念和行为产生改观,但要实现全社会出生性别比的正常化需从根本上改变人们的生育意愿．放弃男孩为首选的生育偏好。这种观念的转变和形成应从社会政策入手和进行调节。根据个体生命周期中不同的个体和社会需求．依靠教育政策、生育政策、社会保障制度、就业政策及退休政策等具体的社会政策对女性和独女户家庭进行关爱和倾斜．通过利益导向创设出生女有福气的生育观和“关爱女孩、尊重女性”的性别价值现。在实施社会政策时,应发挥各项社会政策的灵活性;同时各项社会政策之间应该具有联动性和协调性。此即是社会政策的柔性调节。     

The impact of childhood mortality on Fertility in six rural Thanas of Bangladesh

In this article, we examine the relationship between child mortality and subsequent fertility using prospective longitudinal data on births and childhood deaths occurring to nearly 8000 Bangladeshi mothers observed over the 1982-1993 period, a time of rapid fertility decline. Generalized hazard-regression analyses are employed to assess the effect of infant and child mortality on the hazard of conception, with controls for birth order and maternal age and educational attainment. Results show that childhood mortality reduces the time to subsequent conception if the death occurs within a given interval, representing the combined effect of biological and volitional replacement. The time to conception is also reduced if a childhood death occurs during a prior birth interval, a finding that signifies an effect of volitional replacement of the child that died. Moreover, mortality effects in prior birth intervals are consistent with hypothesized insurance (or hoarding) effects. Interaction of replacement with elapsed time suggests that the volitional impact of child mortality increases as the demographic transition progresses. This volitional effect interacts with sex of index child. Investigation of higher-order interactions suggests that this gender-replacement effect has not changed over time.     

Factors influencing the casefinding of migrations in the Liberian fertility survey

A study was made of the factors that affected the casefinding of internal migrations in Liberia using the Chandrasekar—Deming dual enumeration and tabulation methods. The results of this work suggest that the recording and not recording of a migration is not a random occurrence but is associated with a particular enumeration system, origin and destination of the migration, and the migrant’s age, sex, and location of current residence.     

Ethnic and Birth Weight Differences in Cause-Specific Infant Mortality

This article examines ethnic differences in cause-specific infant mortality, using linked birth and infant death records from a cohort of New Mexican singleton infants, 1980-1983. The research, which applies log-linear analysis, focuses on the combined influences of ethnicity, birth weight, maternal age, and plurality on birth outcomes--that is, on infant survival and deaths due to perinatal, congenital, and respiratory diseases and to sudden infant death syndrome. The results confirm the pronounced impact of birth weight on infant mortality and identify similarities and differences among Anglo, Hispanic, and American Indian babies with respect to cause-specific infant mortality.     

Demographic models of birth outcomes and infant mortality: An alternative measurement approach

Most demographic studies use 2,500 grams of birth weight and 37 weeks of gestation as cutpoints for evaluating the effects of adverse birth outcomes on infant mortality. We propose an alternative strategy, which relies on continuous measures of birth outcomes, identifies an optimal combination of birth weight and gestational age for infant survival, and estimates the effects of adverse birth outcomes in terms of their departure from this "optimal point." We illustrate the advantages of this approach by estimating a logistic model using data from the 1989-1991 NCHS linked birth/infant death files. Finally, we discuss future applications and methodological issues to be resolved in subsequent research.