Fertility rates across the world have been steadily dropping since 1950. Pinpointing the reasons — despite the lack of typical causal conditions such as famine or war — is at the heart of one researcher’s work at the University of Notre Dame.

Lakshmi Iyer, a professor in the Department of Economics, found that there was more to fertility rates than a simple economic or circumstantial explanation. According to her research, people are having fewer children due to cultural factors, with social norms playing a larger role than previously thought.

Popular opinions regarding marriage, contraception and abortion directly impact fertility rates and therefore the demography of a region. This can be particularly true in regions that are predominantly Catholic and where the Church’s teachings have a stronger influence on an individual’s fertility decisions.

“Social norms truly matter when it comes to understanding demography,” said Iyer, who is also a professor of economics and global affairs at Notre Dame’s Keough School of Global Affairs and a faculty fellow at the school’s Kellogg Institute for International Studies and Liu Institute for Asia and Asian Studies. “And we are researching how changing the salience of specific norms is shaping fertility behavior.”

Iyer and her research team examined the impact of visits by Pope John Paul II throughout Latin America between 1979 and 1996. They found that in countries where he gave public speeches that reinforced Catholic social teaching, fertility rates were higher in the long term. Using Demographic and Health Survey (DHS) data on 13 Latin American countries across 16 papal visits, the researchers found that although the pope’s speeches were not intentionally aimed at influencing fertility, his messaging heightened existing Catholic social norms that promote getting married and having families, causing a statistically significant increase in birth rates within those countries.

The findings, which were reported in the working paper “Religion and Demography: Papal Influences on Fertility,” indicated that in the two to five years following the papal visits, an additional 220,000 to 251,000 births occurred in the 13 countries analyzed in the study. Where the pope mentioned marriage or abortion and contraception in his public speech, birth rates jumped the greatest. Where he condemned premarital sex in his homilies, birth rates decreased. Where he spoke about the value of marriage, both marriage and fertility rates increased.

The researchers said the effects of the pope’s messages were felt most strongly by individuals who were not necessarily following the Church’s teachings on these topics; in this case, those in non-Catholic, wealthy and highly educated households.

“These results indicate that people are really listening to what the pope has to say,” Iyer said. “And the topics he addresses really matter.”

Iyer added that not only were the messages important in changing how the audiences viewed their relationship with marriage and family, but so was the fact that it was the pope himself delivering those messages.

“Who the messenger is matters,” Iyer said. “It needs to be someone who can reinforce what is important to the culture. You can change social norms by having a predominant leader remind people of what is considered good and acceptable behavior within that particular society.”

For Latin America at the time of Pope John Paul’s visits, these messages were crucial to help slow down the dramatic decline in birth rates, which went from an average of 5.9 births per woman in 1960 to 2.2 in 2010. For other countries experiencing similar below-replacement fertility rates, Iyer said this type of messaging can help induce people to want to have more children.

And those messages don’t have to be tied to a specific religion or to religious beliefs, Iyer added, but they do need to be relevant to the culture they are addressing and to the existing social norms — and having them delivered by a respected leader only adds to their saliency.

“Cultural ambassadors matter, but only in certain contexts,” Iyer explained. “They are the ones who can speak for those norms, reinforce them or make them more important to people.”

This study exemplifies the kind of population-level research that Notre Dame Population Analytics (ND Pop), a new research initiative at the University, seeks to foster. Many of the issues facing society are demographic — poverty, the aging population and declining fertility, disparities in educational outcomes, family instability and the decline in life expectancy brought about by the drug crises. ND Pop is leveraging the tools of data science to foster impactful research that can inform policy and practice. Iyer’s paper and other recent population study findings are available through ND Pop’s working paper series.

“Who the messenger is matters. It needs to be someone who can reinforce what is important to the culture.”

“Demography is really important to think about in terms of long-term economic or social change,” Iyer said. Aside from policies that promise monetary incentives or better access to child care for families, Iyer and her co-authors believe that a cultural component could also be considered. They acknowledge, however, that further research should be conducted to analyze the effects of other changes in social norms such as increased secularization or changing religious denominations in a country, as well as contrasting these with the effects of government policies and economic incentives.

Iyer conducted her research alongside co-authors Paloma Lopez de mesa Moyano of Emory University and Vivek Moorthy, who received his doctorate from Notre Dame in 2022 and is now at the College of the Holy Cross.

The DHS surveys are nationally representative household surveys conducted in more than 90 countries since the mid-1980s. They collect detailed information from women of child-bearing age about their fertility histories, including a retrospective questionnaire on the month and year of all births. These fertility histories enabled the researchers to construct fertility time series for each woman using a consistent survey methodology and questionnaire across countries.

Contact: Tracy DeStazio, associate director of media relations, 574-631-9958 or tdestazi@nd.edu