(March 2007) We often hear that the U.S. family is shrinking and that more young Americans aren’t getting married or having children—but the U.S. has a higher birth rate than most other industrialized countries. Who is having or not having children in the U.S. today? How has U.S. fertility changed since the baby-boom years of the 1950s and 1960s? How has immigration affected the U.S. birth rate? Where does the U.S. rank compared with other countries?

During a PRB Discuss Online, Mary Kent, editor of PRB’s Population Bulletin, answered participants’ questions about the U.S. birth rate and population growth.


March 22, 2007 1PM EST

Transcript of Questions and Answers

Philip C. Chinn: What are the current fertility rates by racial and or ethnic groups?
Mary Mederios Kent: The total fertility rate (TFR) or average number of children per woman given current birth rates—was 2.1 children per woman in 2005. Among racial and ethnic groups, the TFR for highest for Hispanics at 2.9 children per woman, compared with 1.8 for non-Hispanic whites, 2.0 for non-Hispanic blacks, 1.9 for Asian and Pacific Islanders, and 1.7 for American Indians and Alaska Natives. Among Hispanics, the rates are highest for Mexicans and Central Americans—who are our fastest growing Hispanic groups.

Dr Michael Cook: Hi Ms Kent, Australian data shows that a disproportionate share of the nation’s children are born to women with 3 or more children. As I recall, more than 50 of the total fertility rate is due to the 27% who have 3 or more. Is the situation the same in the US? Where can I get figures? Many thanks.
Mary Mederios Kent: I’m not familiar with Australian birth data, but in the United States, the large majority of annual births are 1st and 2nd births. In 2005, 72 % of U.S. births were first- or second-born children. About 28 percent of babies born had two or more siblings. Thus, the U.S. birth rate is driven by more women having 1 or 2 children, not fewer women having a larger number of children. Among American women ages 40 to 44 in 2004, less than 30 percent had three or more children, while 51 percent had 1 or 2 children. Nineteen percent had never had children. The birth data are easily obtainable from the National Center for Health Statistics website (http://www.cdc.gov/nchs/births.htm). Statistics on the women by the number of children ever born are available from the U.S. Census Bureau’s website (http://www.census.gov/population/www/socdemo/fertility.html)

L. Ritz: Review what is considered the replacement rate for any population.
Mary Mederios Kent: In general terms, a two-child per woman average is considered replacement level—the fertility level at which each couple is replaced in the population by their own children, yielding zero population growth. It must slightly above 2 to account for mortality. In more specific terms, maintaining replacement-level fertility requires that each couple produce a daughter who lives long enough to have her own children. The average number of children per couple, then, must be above two to account for the fact that not all children will survive through their childbearing ages. In addition, because 105 boys are born for every 100 girls, an exact 2-child average would not produce quite enough daughters. In the United States, replacement level is about 2.06 (usually rounded to 2.1). In a higher mortality country, replacement-level fertility would be higher – above 3.0 in some countries—because so more children die before reaching their childbearing ages.

cyndi lee: The vast majority of US population growth is from immigration—post-1970 immigrants and their descendants. The charts at NumbersUSA.com show this quite clearly. Why does PRB go to such lengths to downplay the impact of immigration?
Mary Mederios Kent: Immigration is clearly an important source of population growth in the United States. According to the U.S. Census Bureau, net international migration acounts for between 40 and 45 percent of annual growth in recent years. Researchers calculating the contribution of immigrants and their children to U.S. population growth over the past 30 years or so concluded that these 1st and 2nd generation residents accounted for about 55 percent of growth. Several papers from the Pew Hispanic Center discuss the assumptions behind these estimates. PRB doesn’t downplay the role of immigration, we tend to report the official statistics. Births to non-immigrants are also an important source of population growth.

Boris Denisov: Could you comment on data (if any) of racial dicrepancies in fertility in the US? Especially interesting are proportions childless and never married. best, boris
Mary Mederios Kent: I mentioned the differences in fertility among race and ethnic groups above: Hispanics have the highest, followed by non-Hispanic blacks, non-Hispanic whites, Asians/Pacific Islanders, and American Indians/Alaska Natives. As you might imagine, the percent of women who are childess follow a similar pattern: Among women ages 40 to 44, just 14 percent of Hispanics were childess, compared with around 20 percent of non-Hispanic whites and blacks, and 18 percent of Asians. The percent never married is somewhat different by race primarily because of the high percent of U.S. black women who had not married by age 40-44 (31 percent). And, although HIspanics have higher fertility, they also are somewhat less likely to marry (15 percent). About 10 percent of whites never married. Some of these differences can be tied to educational and income differences, but also to cultural differences among groups.

Dan Gardner: Media commentators often note that the United States has a higher fertility rate than Canada, Britain and other Western countries but the explanations they offer (eg. the US is more religious, therefore…) seem to be shaped by their own preferences or ideology rather than proper research. Can you please explain what demographers believe are the key reasons why the US fertility rate is higher than that of other modern countries?
Mary Mederios Kent: The short answer is that we don’t know why fertility is higher in the U.S. than in Europe and other industrialized countries (or conversely why it sank so low in these countries). It is true the largest U.S. minority group—Hispanics—has much higher fertility than other racial and ethnic groups (about 2.9 children per woman), but this explains just part of the difference. The rate for the U.S. majority population: non-Hispanic whites—was 1.8 in 2005, still well above the national average for Canada and for all but a few European countries, including France and Sweden. In addition to the social aspects you mentioned (maybe Americans are more religious, traditional, family-oriented), some demographers have offered these economic explanations: It is easier for U.S. women to balance children and employment because there are more options for part-time jobs, flexible work schedules, and day care. In addition, there is some evidence that women’s wages are better relative to men’s in the U.S. – so children may be more affordable for American couples. Additional difference between the U.S. and lower-fertility countries that might explain some of the difference: The teen birth-rate, although at an all time low, is higher in the U.S. than these other countries. And,some birth control methods are more easily available in Europe than in the U.S.

Beverly Andrews: Hi Ms Kent, I would like to know what are the current trends in teenage fertility rates if possible by ethnic groups etc. Also is teenage childbearing viewed as a social problem and why? Thank you
Mary Mederios Kent: The teen birth rates have been falling in the U.S. and are now at their lowest levels ever. The rates are highest Puerto Ricans, followed by blacks, and other Hispanic groups. Children born to teen mothers tend to fare less well in school and the job market, and teen mothers often face many obstacles to finishing school and holding down a job. So yes, it is a problem for our society.

Laila Rahman: Does the birth rate vary across different ethnic groups and immigrant population over the period in the US? What are the trends and significant variations, if any?
Mary Mederios Kent: I posted the different fertility rates for ethnic groups above. Regarding immigrants, the forieign born women who were age 40 to 44 in 2005 had higher fertility than native-born women (2.1 children compared with 1.8 children). The national center for Health statistics has recently published a study showing fertility among Hispanic groups—where you can get additional information. As I mentioned above, one of the recent of recent decades has been a narrowing of the gap in fertility rates among black and white Americans.

john crow: how does fertility in illegal families effect our population figures
Mary Mederios Kent: Yes, some of the roughly 12 million illegal immigrants have had children in the US, although a disproportionate share of people here illegally are single and do not have children, according to a recent Pew Hispanic Center report. This report estimated there were about 5 million children in illegal immigrant households in 2005—and about two-thirds of them had been born in the United States. To put this in perspective, the total U.S. child population (defined as under age 18), was about 73 million in 2005, so children born to illegal immigrants account for less than 10 percent of U.S. children. So illegal immigrants do contribute a small amount to U.S. fertility.

Mary G: Why is replacement fertility a TFR of approx. 2.1 rather than 2.0? And how do higher TFRs relate to replacement fertility? Thank you.
Mary Mederios Kent: I posted a long explanation of the replacement level TFR above. The TFR must be above 2.0 to account for the fact that some children die before they reach their childbearing ages, and because there are slightly more boys born than girls (105 boys to 100 girls) — and it is the girls who will produce the next generation.

Hazel Denton: The TFR for Hispanics in the USA is above replacement level, but could it be biased upwards? Reason: if we assume most births are registered, but perhaps not all mothers are counted in the census, the denominator could be biased downwards.
Mary Mederios Kent: The demographers at the National Center for Health Statistics consider possible biases when they calcuate the rates. You might want to look at their website to see if they have dealt with this specific question.

F. González: What can be said about current fertility differentials by educational and income levels in US?
Mary Mederios Kent: Fertility tends to decline as education level increases. Women may put off marriage and children to further their education, then to get established in the labor force. Women age 40 to 44 with no high school education had about 2.5 children in 2004, compared with 1.6 children among women with a graduate or professional degree. Fertility by income follows a similar pattern.

Tyler LePard: Would you please address the anti-immigration & anti-contraception movement’s belief that low birth rates around the world (specifically Europe and the United States) will lead to an aging population and financial problems?
Mary Mederios Kent: Many European countries are already seeing rapid population aging because of decades of very low birth rates. It is unlikley that they could have enough immigration to stave off population aging. An older population will bring some financial challenges because there will be a lower ratio of working age to elderly. Hopefully these countries will find ways to cope with these challenges.

Eve Ulrich: What are the ‘real’ birth projections and percent increases through the next 5-10 years? Every source seems to be different. Can you provide a point of view?
Mary Mederios Kent: The U.S. Census Bureau’s latest projections assume that the U.S. TFR will be between 2.1 and 2.2 from 2005 to 2050. Of course we don’t know what they will be (remember no one predicted the baby boom). The U.S. TFR is unlikely to sink to the lowest levels seen in Europe and East Asia, but it could well decline.

Kantroo Chaman: Aren’t better living conditions, an openness in the society, immigrationetc, responsible for a higher birth rate inspite, of reduced number of marriages? Does not marrying necessarily mean having no children ? Infant mortality rates are also to be taken into account.
Mary Mederios Kent: You are right that many social and economic factors affect a country’s birth rate, and the contribution of fertility to overall population growth. Regarding children born to unmarried women—that has increased to about 37 percent of all births in the U.S., but it is even higher in some European countries. Childbearing outside marriage is especially common among blacks and American Indians—between 63 percent and 70 percent of babies born in 2005 were to unmarried mothers. It is least common among Asian Americans.

John Glad: What is the correlation between fertility and IQ, if only as inferred by demographic parameters that correlate positively or negatively with IQ?
Mary Mederios Kent: There has been a lot of interest in this questions over the years. Much of the apparent link between fertility and intelligence measures were explained by other factors, such as poverty and low levels of education.