Alternative Projections of the U.S. population

The U.S. Bureau of the Census recently released a set of population projections that include middle and high projections that we argue are too conservative. The projections discount the possibility of future baby booms and assume slow rates of mortality decline and low levels of immigration. In this article we explore the impact on the size and age composition of the U.S. population of alternative scenarios of plausible fertility, mortality, and immigration assumptions. We conclude that (1) the Census Bureau's highest projection might be interpreted as a reasonable middle projection, (2) a reasonable high projection would yield a U.S. population in 2080 some 300 million persons larger than the Bureau's highest projection, with the population 85 and older more than twice the Bureau's greatest estimate, and (3) uncertainty about the pace of population growth is substantially greater than the Bureau's projections suggest.     

The Quality of Male Fertility Data in Major U.S. Surveys

Researchers continue to question fathers’ willingness to report their biological children in surveys and the ability of surveys to adequately represent fathers. To address these concerns, this study evaluates the quality of men’s fertility data in the 1979 and 1997 cohorts of the National Longitudinal Survey of Youth (NLSY79 and NLSY97) and in the 2002 National Survey of Family Growth (NSFG). Comparing fertility rates in each survey with population rates based on data from Vital Statistics and the U.S. Census Bureau, we document how the incomplete reporting of births in different surveys varies according to men’s characteristics, including their age, race, marital status, and birth cohort. In addition, we use Monte Carlo simulations based on the NSFG data to demonstrate how birth underreporting biases associations between early parenthood and its antecedents. We find that in the NSFG, roughly four out of five early births were reported; but in the NLSY79 and NLSY97, almost nine-tenths of early births were reported. In all three surveys, incomplete reporting was especially pronounced for nonmarital births. Our results suggest that the quality of male fertility data is strongly linked to survey design and that it has implications for models of early male fertility.     

The changing influence of religion on U.S. fertility: Evidence from rhode Island

Traditionally one of the indisputable generalizations in demography has been that Catholics have higher fertility than Protestants and Jews (Freedman, Whelpton, & Campbell 1959; Ryder & Westoff 1971; Westoff, Potter, & Sagi 1964; Whelpton, Campbell, & Patterson 1966). Recently, however, doubts have been raised about the continued validity of this longstanding and heretofore widely accepted generalization.     

The Census Bureau on Prospects for US Population Growth in the Twenty‐First Century

The U.S. Census Bureau periodically releases projections of the US resident population, detailed by age, sex, race, and Hispanic origin. The most recent of these, issued 13 January 2000, for the first time extend to the year 2100 and also include information on the foreign‐bom population. (Earlier projections were carried up to 2080.) The extensive tabulations presenting the new set, and detailed explanation of the methodology and the assumptions underlying the projections, are accessible at the Census Bureau's web site: http://www.census.gov . A brief summary of some of the main results of these projections is reproduced below from United States Department of Commerce News, Washington, DC 20230. (The Census Bureau is an agency of the Department of Commerce.) Uncertainties as to future trends in fertility, mortality, and net migration over a period of some 100 years are very great, as is illustrated by the massive difference in the projected size of the population for 2100 in the three variants produced. The “middle” projected population figure of 571 million (which represents a growth of some 109 percent over its current level) is bracketed by “lowest” and “highest” alternative projections of 283 million and 1.18 billion, respectively. With somewhat lesser force, the point also applies to the 50‐year time span considered in the well‐known country‐by‐country projections of the United Nations. These projections are also detailed in three variants: low, middle, and high. The UN projections (last revised in 1998) envisage less rapid growth in the United States during the first part of the twenty‐first century than do the Census Bureau's. The projected population figures for 2050 in the three variants (low, middle, and high) are as follows (in millions):

Low fertility due to delay in -- not dearth of -- births

Population Council demographer John Bongaarts and his colleague Griffith Feeney argue that recent concern about a lack of births overlooks the fact that many women in developed countries are simply choosing to bear children later than women used to. So-called birth dearths are often caused by temporary delays in childbearing. The two demographers have designed a new way for demographers to account for the timing, or tempo, of childbearing in estimates of fertility. Their tempo-adjusted total fertility rate (TFR) allows demographers to correct skewed fertility trends, such as those leading to projections of birth dearths. The new measure provides a better indication of women's true propensity to bear children. Standard measures of fertility are distorted by changes in tempo. Such changes occur when large numbers of couples delay or accelerate their initiation of family building. The authors used historical data and theoretical arguments to validate the tempo-adjusted TFR, which improves upon the two common measures of fertility. Flaws in the TFR and the completed fertility rate (CFR) are corrected by Bongaarts and Feeney's new measure. To demonstrate their new tool, they examined the below-replacement fertility seen in recent decades in the US. By the mid-1990s, the TFR in almost every developed country had fallen below the replacement level of 2.1 births/woman, and in Italy, Spain, and Germany it fell below 1.5. If such fertility persists, declining population size, extreme population aging, and financial pressure upon social security systems may result. However, if fertility preferences hold at current levels, the very low fertility rates observed in the developed world will approach 2 children/couple.     

Comparing alternative statistics on recent fertility trends in Australia

In recent years fertility statistics in the Australian Bureau of Statistics (ABS) publication Births, Australia have suffered from a number of issues, including delayed receipt of registration data from the Registrars and computer processing errors. They prompt questions about the quality of these statistics for measuring the level of fertility and its year-to-year changes. The aim of this paper is to compare three sets of fertility statistics, (1) ABS birth registrations, (2) ABS births by year of occurrence, and (3) births in the Australian Institute of Health and Welfare National Perinatal Data Collection (NPDC), at the national and state/territory scales. Annual births by state/territory of usual residence from the three data sources were obtained for the period 2004–2013 or 2004–2014. Recast Estimated Resident Populations from the ABS were used to calculate Total Fertility Rates. For some states and territories there are non-trivial differences in fertility as recorded by the three data sources. In Queensland the trend in fertility according to ABS birth registrations is quite different from that based on the NPDC; in Tasmania and the Northern Territory birth registrations exceed NPDC births by a notable margin. There appears to be more uncertainty about the levels and annual changes in Australian fertility than many users of the data may realise. All three fertility datasets seem to possess some limitations. It is suggested that a new Australian fertility database be created which employs data linkage to incorporate both birth registrations and perinatal data.     

What's happening to U.S. family size?

A telephone survey by Zero Population Growth demographers found that birthrates have risen slightly for the 1st quarter of 1977. Average estimated family size is now 1.85 children per women compared with 1.77 for the 1st quarter of 1976. For all of 1976 the total fertility rate was 1.76 children per woman. It is predicted, on the basis of the informal survey, that the total fertility rate will rise to 2.0 or 2.1 children by the early or mid-1980s. In 1976, married women expected an average of 2.4 children each. Wives 18-24 expected 2.1 children each while older women (35-39) expected 3.0. Many women are delaying births. Wives 18-24 have an average of .8 children each, wives 25-29 have 1.6 children each. Campbell Gibson, former chief of the projections branch of the Census Bureau, believes births will not reach levels of expectations becuase of the financial, employment, and social problems the huge Baby Boom age group faces throughout its lifetime. The undecided women in the surveys reduce the predictive value. 18% of single women aged 14-39 and 8% of married women in the same age group said they were uncertain about how many children they would have. Since the personalitites and motivations of this undecided group are similar to those who expect to remain childless, it is possible that this group will have fewer children. Such nondemographic factors as media publicity about low fertility rates may inspire some couples to have children. Conversely, the postponement of births may enable couples to become comfortable with a certain lifestyle and these couples may not have as many children as they expect. Social norms are already changing. The percent of wives expecting to be childless rose from 1.3 to 4.1% between 1967-1975. Those expecting only 1 child rose from 6.1 to 11.2%.     

A fertility analysis of New Zealand marriage cohorts

New Zealand annual returns of non-Maori live legitimate births 1913 to 1955 were tabulated longitudinally by marriage duration and birth order. The figures were used as numerators of fertility rates of forty marriage cohorts, specific for duration and birth order ; the twenty-four oldest cohorts had virtually completed fertility. For the denominators of the rates, the cohorts of initial size (estimated by a method similar to that described by P. H. Karmel) were survived by observing changes over time through divorce, death, widowhood, war-widowhood, and net external migration. The aim was to provide a set of data of the best possible approximation on variations of cohort fertility.

Total cohort rates, cumulated for twenty years’ duration of marriage, and segmental rates of relevant sub-periods are given for parities o to 7+. Total rates of the cohorts of completed fertility yielded values of family size, and were also used for parity progression ratios (by L. Henry’s formula). Segmental rates permitted a study of changes in timing maternities.

The analysis, which needs as a corollary a nuptiality analysis, is concerned, so far with past experience. It confirms the decline in number and proportion of large families. Both the parity progression ratios, and segmental rates of cohorts of as yet incomplete fertility, suggest some recent recovery in three- and fourchild families. For total fertility, such recovery might even be more significant than the observed decline in large families. On the other hand, birth-order specific changes in timing suggest lengthening of intervals among older cohorts as a trend upon which is superimposed the fluctuation due to postponement of, and recovery of a portion of postponed maternities. A construction of hypothetical timing patterns for incomplete cohorts by a simplified method of projection does not lead very far without support of observations on spacing that differentiate for family size.     

Recent net alien immigration to the United States: Its impact on population growth and native fertility

Estimates of the size and structure of recent alien immigration to the United States are made. Substituting these revised estimates in the Series II projections of the U.S. Bureau of the Census implies a future U.S. population smaller than that implied by the Census Bureau’s estimates of immigration. The analysis of Coale (1972)—which calculates the decline in native-born fertility required to accommodate immigration and, at the same time, maintain a stationary population—is replicated, using both the Census Bureau’s estimates and the revised estimates reported here. The revised estimates indicate a smaller reduction in native fertility and a smaller ultimate size of the stationary population than are implied by the Census Bureau’s immigration estimates. The importance of age structure in all of these calculations is demonstrated.     

Assesssing Cohort Birth Expectations Data from the Current Population Survey, 1971–1981

Data from the fertility supplements to the Current Population Survey from 1971 to 1981 indicate that in the aggregate, the lifetime birth expectations of married women 18 to 39 years old in 1971 will closely approximate their completed cohort fertility. During this period, the youngest group of women, 18 to 24 years old, delayed their childbearing; their short-term expectations (1971–76) were not realized, but they made up enough births in the latter half of the decade to enable them to attain their lifetime birth expectations. In retrospect, the “failure” of birth expectations data to predict the “period” fertility downswing in the 1970s resulted not from poor predictions of married women, but rather from unanticipated marital and subsequent childbearing patterns of women who were single at the beginning of the decade. The authors conclude that birth expectations are useful predictors of completed cohort fertility, if adjustments are made to incorporate changes in the proportions married within the birth cohort.     

Evidence bearing on the construct validity of "ideal family size"

George Gallup polled "ideal family size" in 1936 and introduced a concept which subsequently appeared in many polls and fertility surveys. Previous research shows that ideal is a poor measure of respondent's personal fertility plans or behavior and that among researchers there is little agreement about what ideal family size does measure, if anything. Construct validity analysis based on historical, trend, and cross-sectional data suggests that the late 1960s saw ideal politicized as preoccupation with the "population problem" grew. Ideal family size is now appropriately regarded as a measure of a societal pronatalist norm and not merely a projected fertility preference.A version of this paper was presented at the meetings of the Society for Applied Anthropology, Merida, Mexico, 5 April 1978. Data on ideal family size from Blake (1974) are used with permission of the editors ofDemography. Other data come from the 1965 and 1970 National Fertility Studies co-directed by N.B. Ryder and C.F. Westoff (under contract No. PH-43-65-1048 with the National Institute of Child Health and Human Development).     

Estimating marital fertility rates by educational attainment using a survey of new mothers

Marital fertility rates by educational attainment of mother are estimated for the United States for 1963. These calculations are based upon information collected in a probability sample survey of women having births in 1963 and are prepared by relating birth estimates for educational attainment groups to estimates of married women in corresponding groups.The rates do not display a negative association between educational attainment and the annual level of fertility, thus differing from the pattern observed in other measures of period fertility. Women who completed some high school but did not graduate and women with one or more years of college had higher annual fertility rates than women in other attainment classes.Alternative estimation procedures are discussed which illustrate difficulties in obtaining satisfactory correspondence between two independent surveys which are used to obtain the rate calculation components.     

The Long-Term Effect of the Timing of Fertility Decline on Population Size

Existing long-range population projections imply that the timing of the fertility transition has a relatively unimportant effect on long-term population size when compared with the impact of the level at which fertility is assumed eventually to stabilize. However, this note shows that the effect of the timing of fertility decline is a function of the eventual fertility rate: the lower the eventual fertility rate, the greater the effect of the timing of the transition becomes. This finding has important implications for projection methodology, as well as for policies related to the consequences of long-term levels of population size.     

Prospects for fertility reduction and projections for future population growth in Kenya

In 1979 Kenya's annual rate of natural population growth was 3.8%. Data from the1989 Kenya Demographic and Health Survey indicate that significant decreases in fertility levels were experienced during the 1980s. Factors associated with conditions supportive of high fertility in Kenya are discussed, and progress toward attaining significant fertility reduction thresholds during the 1980s is assessed. Findings from recent fertility surveys are presented, and 1969–1989 national level family planning data are evaluated. Four population projections for 1985–2025 are presented and analyzed. One projection is based on official government growth targets; two are based on estimates provided by the United Nations and the Population Reference Bureau, and a fourth projection is based on the assumption that Kenya will attain an annual natural population growth rate of less than 1% by the year 2025. Each projection assumes that fertility declines will be experienced. Kenya's prospects for reducing the annual population growth rate to 1% within the next sixty years and a cost-sharing development policy are addressed briefly in the concluding section. Recent data suggest that Kenya will probably not complete the demographic transition before the year 2050, but Kenya should continue to move through the transition stage.     

Developing strategies for deriving small population fertility rates

Many agencies require population estimates and projections by ethnic group. These projections need ethnic-specific, age-specific fertility rates (ASFRs) but their inclusion is challenging since ethnicity is not recorded at birth registration. In this paper maternity data are used in a case study of electoral wards in Bradford, West Yorkshire, to develop fertility rates for small populations for a 1991 based projection. The challenge is to capture local variations in fertility by ethnic group when data are sparse. Small areas were grouped together using cluster analysis to define combinations with similar sociodemographic and fertility experiences so that sparse data could be aggregated to estimate reliable ethnic-specific fertility rates. For comparison, the data were aggregated into the 1991 Office for National Statistics area type classification. Fertility rates by single year of age for all area types were smoothed using the Hadwiger function. For the White ethnic group there were sufficient births to create ethnic-specific, ward-level ASFRs. For other ethnicities grouping of areas was necessary. The accuracy of the ASFRs in predicting births was assessed using mean absolute percentage error. Results show that for some minority groups district-level ethnic-specific fertility rates produced the most accurate birth estimates even though they were based on a larger area. This implies that rates created may be informative about the local area for White ethnic type but not in the same way for smaller ethnic groups. In terms of grouping strategies we recommend that existing classifications are assessed to determine how well variations in rates are stratified before embarking on a custom scheme. Where population sub-groups are small in some areas, it may be more reliable to use rates derived for larger areas and apply these to local populations. Inevitably, the rates used in a projection are a compromise but hopefully will still capture important dimensions of population change.     

New household projections for the united states

This paper reviews the methods used to prepare the new household projections for the United States that were recently issued by the Bureau of the Census and examines the effect on the resulting number of households of the assumptions made about future marriages and future proportions of household heads in the population.One population projection series was used, since all series are identical for the adult population. Marriage assumptions were generated by assuming various outcomes of the marriage squeeze (defined as the excess of females relative to the number of males in the main ages at marriage in the next few years). Assumptions about proportions of household heads were generated by assuming, in varying degrees, continuation of recent trends in these proportions.Projected changes in marriage and in the proportions of household heads in the population account for one-fourth to one-third of the projected increase in the number of households; the remaining increase is attributable to projected changes in the size and structure of the adult population. Varying the assumed proportions of household heads produces greater differences in the projected total number of households than does varying the marriage assumptions used here. Nevertheless, the various possible outcomes of the marriage squeeze, as represented by the assumptions used, produce significantly different projections of increases in the number of young husband-wife households.The most striking finding is that by 1985, proportions of household heads among the population not "married, spouse present" may well rise to such a level that over the long term, the smaller the number of persons who marry, the larger will be the number of households.     

Income and fertility: The elusive relationship

This paper uses longitudinal data for 1962–1977 to examine the relationship of husband’s income to 1962 expected fertility, to final parity, and to the discrepancy between initial expectations and final parity, separately for four groups of women who in 1962 either had just given birth to a first, second, or fourth child or had just been married. Although economic reasons frequently were cited in 1977 for downward revisions in family size goals, husband’s income was not positively related to fertility in three of the four parity groups. For the merged sample, excluding women with unwanted births, husband’s income showed a small positive relationship to completed fertility.     

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.     

Migrant fertility in Ghana: selection versus adaptation and disruption as causal mechanisms

The aim of the study presented in this paper is to disentangle the roles of three mechanisms -- selection, adaptation, and disruption -- in influencing migrant fertility in Ghana. Using data from the 1998 Ghana Demographic and Health Survey, we fit Poisson and sequential logit regression models to discern the effects of the above mechanisms on cumulative fertility and annual probabilities of birth. Characteristics of migrants from four types of migration stream are examined and compared with those of non-migrants at origin and destination. We find substantial support for the selection hypothesis among both rural-urban and urban-rural migrants. Disruption is evident only in the fertility timing of second and higher-order births in Ghana. Our finding that migrants bear children at about the same rates as the natives at destination implies that the growth rate of cities will slow down quickly and that the rural population will continue to have high fertility. Thus to achieve a reduction in the national fertility level, family planning activities need to be directed towards rural areas.     

Individual and aggregate influences on the age at first birth

This study examines the role of both individual adolescent expectations of market and nonmarket income and aggregate influences on first birth timing for Blacks and Whites and for three birth cohorts of American women. Using two panels of the National Longitudinal surveys, results suggest that between-race differences in age at first birth result from differences in individual expectations about market and nonmarket income. Cohort differences in age at first birth result from relationship differences in both individual and aggregate influences, with aggregate influences differentially altering the role of individual expectations on first birth timing. These results suggest that employment policies that reduce poverty and increase wages would effectively delay childbearing. For Blacks, since early childbearing results from lower expectations about future economic success, similar fertility timing patterns between the races would result if Blacks had White employment and wage levels. Over time, these employment and wage policies will not only alter individual expectations about economic success but also will alter the impact of expectations on fertility timing.