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.     

Fertility patterns among religious groups in Canada

The U shape that has been traced out by the crude birth rate in the United States and Canada is well known. Falling birth rates reached a low point in the mid-1930’s; the rate rose to a peak in 1947 and remained high through the 1950’s. In terms of cohorts, completed family size was smallest for women born around 1910, whose childbearing was concentrated in the 1930’s. With data from the 1961 census of Canada, trends in cohort marital fertility by religion are examined. The U pattern appears for both Protestants and Jews. For Catholics, a reversal in the downward trend of family size had not appeared by 1961, although the U pattern can be discerned for some subgroups such as Catholics living in big cities and persons of Irish ancestry. In the United States, however, changes in family size for all three religious groups and both whites and nonwhites follow the U pattern. Religious differentials in family size in Canada have been decreasing, but they remain much larger than either religious or color differentials in the United States, which show no decrease. The distinctive features of Catholic fertility in Canada are most pronounced among the regionallyconcentrated French Canadians, suggesting an interplay of religious, regional, and ethnic influences.     

Maybe Next Month? Temperature Shocks and Dynamic Adjustments in Birth Rates

We estimate the effects of temperature shocks on birth rates in the United States between 1931 and 2010. We find that days with a mean temperature above 80°F cause a large decline in birth rates 8 to 10 months later. Unlike prior studies, we demonstrate that the initial decline is followed by a partial rebound in births over the next few months, implying that populations mitigate some of the fertility cost by shifting conception month. This shift helps explain the observed peak in late-summer births in the United States. We also present new evidence that hot weather most likely harms fertility via reproductive health as opposed to sexual activity. Historical evidence suggests that air conditioning could be used to substantially offset the fertility costs of high temperatures.     

Seasonality of fertility: New evidence

This paper presents evidence that the seasonal pattern of American fertility applies to nonwhites as well as whites. The patterns are also changing in the same way over time: the summer trough in births is shrinking in magnitude, and the spread of airconditioning, reducing the heat of summer, can explain this shrinkage. The summer hypothesis is further buttressed by evidence, for the total population, that summer temperature extremes can explain a significant portion of the variation around the seasonal trend, in both the North and South. These temperature-induced variations appear to be offset within seven months of their occurrence.This research was supported in part by a grant from the National Institute of Child Health and Human Development. Dennis Sullivan made a number of valuable critical comments on an earlier draft of this paper. Valuable research assistance was provided by Amy Powell and Robert Schoeni.     

Seasonality of coitus and seasonality of birth

Seasonal variation of birth rates has been observed in every population in which it has been studied. Many hypotheses have been advanced to account for the variation, including seasonal variation in frequency of coitus. This relationship is known to be true for other primates, but seasonal variation in coital rate has not been previously documented in man.This paper presents over one hundred woman-years of data on coital rates from about .fifty white, mostly well-educated, premenopausal, married, husband-present volunteers. Seasonal fluctuations were seen in coital rates, of about the same magnitude as seasonal variations in the white birth rates reported for New York City, 1962-64; for the United States, 1963; and for the highest socioeconomic quintile census tracts, Baltimore, 1952-56. However, shifting the birth rates back forty weeks to approximate conception dates revealed no association with the observed coital rates.If the pattern presented has great generality, seasonal variations in births cannot be explained by seasonality of coitus.     

Simulating the Effects of Acculturation and Return Migration on the Maternal and Infant Health of Mexican Immigrants in the United States: A Research Note

A significant body of research on minority health shows that although Latino immigrants experience unexpectedly favorable outcomes in maternal and infant health, this advantage deteriorates with increased time of residence in the United States. This study evaluates the underlying assumptions of two competing hypotheses that explain this paradox. The first hypothesis attributes this deterioration to possible negative effects of acculturation and behavioral adjustments made by immigrants while living in the United States, and the second hypothesis attributes this deterioration to the mechanism of selective return migration. Hypothetical probabilistic models are simulated for assessing the relationship between duration and birth outcomes based on the assumptions of these two hypotheses. The results are compared with the empirical research on the maternal and infant health of first-generation, Mexican-origin immigrant women in the United States. The analysis provides evidence that a curvilinear pattern of duration and birth outcomes can be explained by the joint effects of both acculturation and selective return migration in which the former affects health status over the longer durations, and the latter affects health status at shorter durations.     

The applicability of the burgess zonal hypothesis to urban Canada

A replication for Canada of Schnore's studies of socio-economic differentiation between United States central cities and suburbs produces generally similar results, although the Canadian patterns are by no means as pronounced or conclusive. Older, larger and highly suburbanized Canadian areas are most apt to have high-status groups over-represented in the suburbs and low-status groups over-represented in the central city. Furthermore, this pattern of socio-economic differentiation is found less often in Canadian areas than in the United States areas which tend to be older and larger. A study of change over time also suggests a movement toward socio-economic differentiation between city and suburb. These results are consistent with the Burgess zonal hypothesis which argues that lower-status groups increasingly inhabit the central section and upperstatus groups the outskirts as cities grow.     

Immigration,skills and the labor market: International evidence

Using the 1994–1998 International Adult Literacy Survey, this paper compares cognitive skills and employment of immigrants in Canada, New Zealand, Switzerland, and the United States. Immigrants had lower cognitive test scores than natives in each country, with the largest gaps in the US, and small gaps in Canada and New Zealand. Male immigrants in the US were no less likely to work than natives, while in the other countries, male immigrants were less likely to be employed. Female immigrants were less likely in each country to be employed than natives, with an especially large gap for the US.The author thanks Francine D. Blau and two anonymous referees for helpful comments and suggestions and Katsuhide Yamashita for excellent research assistance. Responsible editor: Christoph M. Schmidt.     

Distinctive features of age-specific fertility profiles in the English-speaking world: common patterns in Australia,Canada, New Zealand and the United States, 1970-98

The paper seeks to identify common features in the fertility patterns of the English-speaking world and provide a model basis for comparison of fertility between countries and over time. Attention is focused on the heterogeneity within the fertility patterns of Australia, Canada, New Zealand, and the United States, similar to that reported earlier for the UK and the Irish Republic. The recent age-specific fertility patterns of these countries display a marked 'bulge' in fertility of women under age 25. A mixture model with two-component Hadwiger functions provides a suitable fit. The heterogeneity thus suggested is related to the proportion of births outside marriage. Additionally, there is some evidence that, in the United States, and lesser extent in New Zealand, this heterogeneity in fertility patterns may be explained by ethnic difference in the timing and number of births.     

The longevity of Jews in Canada, 1940–1942

A life table for the Jewish population of Canada, based upon their mortality experience during 1940–2, yielded an average length of life (expectation of life at birth) of 67–53 years for males and 69·89 years for females. These figures are greater than those for the general population of Canada by 4·58 years for males and 3·60 years for females. These margins decrease with advance in age; the expectations of life for Jews and for the total Canadian population are equal at age 25 in the case of females, and at age 35 in the case of males.

Jewish infants in Canada start life with a mortality rate, in the first year, only two-fifths of that for the general population. This advantage for Jews is observed through childhood, adolescence, and early maturity. However, the margin between the Jewish and total populations decreased with advance in age until, shortly after age 50, the Jews begin to show the higher mortality rates.

The Jewish populations of the United States and of Canada have great similarities in their social and economic structures. They also share, very largely, in their European origins, and they have come to North America during the same period. It is, therefore, a fair assumption that the longevity and mortality characteristics of the relatively small Jewish population of Canada may be indicative of what might be found for the millions of Jews in the United States, for whom such information is not available.     

Health and Other Aspects of the Quality of Life of Older People

Celebrating the United Nations' International Year of Older Persons, in September 1999 a survey research project was undertaken throughout the Northern Interior Health Region (NIHR) of British Columbia. A total of 875 people completed 23-page questionnaires, the average age of the respondents was 69 and the range ran from 55 to 95 years. Responses to the SF-36 questionnaire indicated that for male respondents aged 55–64, the mean score for the 8 dimensions was 74.4. This mean was practically identical to that of the United States norm for such people (74.5) and lower than that for the United Kingdom (77.4). For male respondents aged 65 and older, the mean was 68.3. This was numerically higher but again practically the same as that of the norm for the United States (68.1). For females aged 55–64, the mean score for 8 dimensions was 73. This was superior to that of the United States norm of (70.6) for such people and lower than that for the United Kingdom (74.6). For female respondents aged 65 and older, the mean score was 65.4. This was practically identical to that of the United States (65.5).Comparing 18 average figures for our respondents on satisfaction with specific domains of life (e.g., financial security, health, friendships) and life as a whole with those of average adults in Prince George in November 1999, we found that in all but two cases the older people's scores were higher. Only in the cases of satisfaction with health and overall happiness were older people's scores lower, and the differences were not statistically significant.Eleven percent of our respondents reported that they had been a victim of a crime in the last year, compared to 38% in our 1997 adult victimization survey. Older people had a more benign view than ordinary adults of the growth of crime in their neighbourhood and city, although exactly 64% of both groups thought that crime had increased in Canada. Although older people had a more optimistic view than other adults of the increase in crime in their neighbourhoods, fewer of the former than the latter felt safe out at night. Nevertheless, compared to adults surveyed in 1997, the behaviour of respondents in our survey of older people was not as constrained by concerns of criminal victimization.Two or three of the 8 SF-36 health dimensions explained 37% of the variation in life satisfaction scores, 34% of variation in happiness scores, 34% in satisfaction with the overall quality of life scores and 22% in satisfaction with one's overall standard of living. In every case, Mental Health was the dimension that had the greatest impact on our four dependent variables.When all of our potential predictors were entered into a regression equation simultaneously, we found that they could explain 60% of the variance in life satisfaction scores, 44% in happiness scores, 58% in satisfaction with the overall quality of life scores and 59% in satisfaction with one's overall standard of living scores.     

A cohort analysis of Korean immigrants' class backgrounds and socioeconomic status in the United States

"In this article, I first survey briefly the history of Korean immigration to the United States from 1903 to the present. Second, I explain the motivations and entry mechanisms that brought Korean immigrants into the United States. Third, I document and explain the changes in the class backgrounds of Korean immigrants during the last three decades. Finally, I examine how such changes have affected the patterns of social and economic adaptation among the different waves of immigrants."     

Health Endowment at Birth and Variation in Intergenerational Economic Mobility: Evidence From U.S. County Birth Cohorts

New estimates of intergenerational economic mobility reveal substantial variation in the spatial distribution of opportunity in the United States. Efforts to explain this variation in economic mobility have conspicuously omitted health despite it being a key pathway for the transmission of economic position across generations. We begin to fill this gap in the literature by examining the relationship between health endowment at birth and intergenerational economic mobility across county birth cohorts in the United States, drawing on estimates from two population-level data sets. Exploiting variation across counties and over time, we find a negative relationship between the incidence of low-weight births and the level of economic mobility as measured in adulthood for the county birth cohorts in our sample. Our results build on a large and growing literature detailing the role of early childhood health in the transmission of economic status across generations and suggest that the incidence of low-weight births is negatively associated with intergenerational economic mobility.     

Infant Mortality in Nine Industrial Parishes in Northern England, 1813–1836

Evidence about infant mortality in a number of industrial towns was derived from baptismal and burial registers of the Anglican Church. The level of infant mortality during the period 1813–1836, after correction for underregistration, was comparable to that of British towns during the second half of the century. Infant mortality increased during this period, perhaps as a reflection of rapid population growth. In each of the parishes a winter peak and a summer trough was found in the seasonal index of infant deaths during this period. This pattern is very different from the high summer mortality that prevailed in British towns during the late nineteenth century. However, mortality in the summer increased over time, thus reducing the depth of the summer trough in infant deaths, and perhaps represents a movement towards the summer peak so apparent later in the century.     

A demonstration of the effect of seasonal migration on fertility

Fertility estimates were calculated using own children data from the Mexican migrant town of Guadalupe, Michoacan. In this town, 75 percent of families have a member working in the United States, and wives are often regularly separated from their migrant husbands. Simulations by Menken (1979) and Bongaarts and Potter (1979) suggest that fertility among these women should be depressed. Our results confirmed this hypothesis, showing that the seasonal absence of migrant husbands disrupted both the level and timing of fertility. However, the effect was greater for legal than for illegal migrants, a pattern that stemmed from social factors as well as physical separation. A logistic regression analysis showed that reductions in birth probabilities are greater the longer a couple is separated, and that these reductions are in the range expected from prior simulations.     

The flood control saga in the Passaic River Basin

Flooding is a natural phenomenon which engineers and politicians have attempted to control since the beginning of time. The Passaic River Basin in northern New Jersey has been recognized as a significant floodprone area in the United States since colonial times. Several State and U.S. Army Corps of Engineers proposals have been abandoned because of both economic and environmental objections to expensive public works projects. During the early part of the Twentieth Century, houses were built in the floodway of the Passaic River, an area where lives and personal belongings were at highest risk.The Army Corps of Engineers has proposed a $1.0 billion flood control tunnel plan while a local watershed association, the Passaic River Coalition, has recommmended a buy-out of the houses at highest risk at a cost of $103 million. This paper introduces that innovative concept for flood management—relocating people out of the rivers path—in the most urban area in the United States.     

Seasonal fertility cycles in rural Egypt: Behavioral and biological linkages

The annual birth cycle in rural Egypt peaks in December and has two distinguishable minima in June and September. This pattern bears a striking inverse resemblance to the seasonal movements of employment and wages. Infant and child mortality and marriage also display stable, though different seasonal patterns. The paper explores whether the correlation between labor demand, mortality events and fertility reflect some causal behavioral relationship. It is shown that the probability of a birth is lower in months with high opportunity cost of time. Direct replacement is a significant phenomenon in rural Egypt and it occurs fairly quickly.     

Sexual orientation and gender identity in North America: legal trends, legal contrasts

The article provides a comparative analysis of recent legal developments with regard to LGBT rights in Canada and the United States of America. Both countries have made great progress towards better protection and full recognition of LGBT rights. Despite this progress, Canada appears to be ahead of the United States, as illustrated by two most recent court decisions (e.g. Halpern, legalizing same-sex marriage in Ontario, and Lawrence v. Texas, decriminalizing consensual sodomy in the United States).     

Emigration from Canada in the 1960s

Summary Emigration from Canada can be assessed only by indirect means. Here, survival ratios have been applied to the total population enumerated in the 1961 Census and to particular segments of it, so that a comparison of the calculated numbers in 1971 with the population actually enumerated indicates the volume of emigration during the decade, both in the whole population and in certain groups. Amounting to two-thirds of the number of immigrants during the same period, the estimate for the ten years is exactly double the volume of emigration reported to the Joint Parliamentary Committee on immigration policy of 1975. Since 1971, the level of emigration has probably fallen. Of the 960,000 emigrants during the decade, 42 per cent were Canadian-born. Their favourite destination was the United States; immigrants, on the other hand, tended to return home. Many immigrants now stay in Canada for only a few years. Fewer Canadians emigrate to the United States. These two factors have contributed to a new pattern of emigration, up-to-date details of which will not be ascertained before the Census of 1981.     

Application of Granger-Sims causality tests to monthly fertility data, 1958–1984

When applied to monthly age specific data, Granger-Sims causality tests provide a useful technique for identifying the effective lag between business cycles and fertility in the United States. Male and female monthly age specific unemployment rates are used as a proxy for the business cycle, and test results are presented for first and higher order birth rates, as well as total age-specific monthly fertility rates. The period is subdivided (January 1958 – May 1973 and June 1973 – December 1984) in order to identify possible trends. Four results hold in all cases studied, with respect to the relationship between unemployment and fertility. (1) Noncausality is rejected in the direction from unemployment to fertility, and no feedback effect is indicated; thus the relationship is one of simple causality. (2) In the critical decision period from 9–16 months prior to realized fertility rates, the sign of the effect of unemployment on fertility is negative: this holds for both male and female unemployment rates. (3) There appears to have been a shortening of the effective lag between unemployment and fertility, of perhaps 2 – 3 months, between periods 1 (1959 – 1973) and 2 (1973 – 1984). (5) The strength of the (negative) relationship between unemployment and fertility appears to have increased from period 1 to period 2.Presented at the annual meeting of the Population Association of America, Chicago, April 30, 1987. This paper has benefitted from discussions with and comments by Andrew Weiss, Clive Granger, Lee Ohanian and Pietro Balestra, and from comments by two anonymous referees. For help in obtaining previously unpublished data, the authors are grateful to Stephanie Ventura (NCHS), G. P. Goings (BLS) and Paula Schneider (Bureau of the Census). Financial support was provided by the University of Southern California