In the United States, the total fertility rate — the number of children a woman has in her lifetime — fell from seven or eight in 1800 to slightly more than two today, says J. David Hacker, assistant professor of history at Binghamton University. And with a five-year $667,237 grant from the National Institute of Child Health and Human Development, Hacker hopes to find out why.
"It's one of the most profound social revolutions of the period," he said. "It has all kinds of ramifications for the social and economic history of the United States, including women's ability to participate in the paid labor force, parental resources available for children's education, the age structure of the population and even the future of the social welfare state."
Declining fertility in that period was a major factor in the aging of the population. The median age of Americans rose from less than 16 years in 1850 to older than 35 in 2000, Hacker said. It is projected to reach 39.1 years in 2035.
"What's interesting about the fertility decline is that the vast majority of it takes place before there's modern contraceptive technology," Hacker said. "It's kind of ironic. Our best source of data on fertility — the U.S. birth registration system — was not in place until 1933, but at that point we've had almost 100 years of continuous decline in the birth rate."
For that reason, Hacker's quantitative study will rely primarily on data from the U.S. Census Bureau. He will describe the fertility decline in greater detail than previously possible, looking at differentials such as race, ethnicity, region and occupation. He will also explain the decline using multi-level empirical models.
"The census is quite rich," he said. "I am employing a method of analysis called Own Child Fertility Methods, which allows me to look at women's childbearing experience and correlate that with individual and household-level data that's available in the population census and with county-level data available in the agriculture and manufacturing censuses.
There's a split in the literature about the fertility decline, Hacker notes. Economists argue that factors such as a decrease in available farmland, industrialization, urbanization and the rising costs of children are key causes. Social historians point more to culture and women's status and role in the household. Hacker's study is designed to address both of those viewpoints.
Hacker has pioneered the creation of cultural variables in the census to correlate with the fertility decline. He tracks child-naming practices as a proxy measure of parental religiosity, for instance. During the 19th century, he notes, there was an amazing secularization of the naming pool. Three-quarters of all children's names had biblical origins in 1800, while by 1920 just a fifth had such origins.
"What I've shown," Hacker said, "is that parents who rely on biblical names for their children have much larger families than parents who rely on secular names, controlling for economic and other factors."
The 15 census microdata samples Hacker will examine include records for some 18 million individuals. "Computer technology has really aided the kind of research I conduct," Hacker said. "There's no way you could have analyzed 18 million cases — just 10 years ago it would've been difficult."
According to Hacker, many countries have experienced or are experiencing a demographic transition from high birth rates and high death rates to low birth rates and low death rates.
"The United States is in some ways an ideal laboratory to study this both because it appears to be quite early in the adoption of conscious family-limitation practices and because of the heterogeneity of the population and its large-scale immigration."
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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