Mistaken Identity

This past August, Professor of Sociology Emilio Parrado was part of a team awarded a $500,000 grant from the National Institutes of Health and the National Institute of Child Health and Human Development to study the interaction between immigration and fertility. Using existing population data and new analytics methods, Parrado, also the department chair, seeks to refine the way U.S. policy is informed. We sat down with him to discuss the complex dynamics involved in charting the make-up of a population.

Blake Cole: How do you hope to improve on modern demography methodologies?

Emilio Parrado: It’s about strengthening the connections between demographic processes. Demography is founded on three tenets: fertility, mortality, and migration. Migration has always been kind of tacked on, not systematically integrated with the other tools. And it has always been the case that all these processes are treated as separate, meaning under this model that what happens with fertility doesn’t affect mortality and doesn’t affect migration. This is a problem because, more and more, developed societies are affected by international migration, so we don’t have good models to really assess how migration affects the population of receiving societies in terms of fertility.

BC: How are fertility and migration related?

EP: We always thought that fertility rates and migration rates were independent, so even if migration changed, fertility rates were going to stay the same. But that’s not what we’re finding. When migration is reduced, fertility rates in the U.S. go down. When migration is increased, fertility rates go up. This is crucial for formulating better projections of the U.S. population. It’s also important for understanding the fertility behavior of groups that have a significant number of immigrants. Applying methods that have been developed for populations that don’t have many immigrants produces distorted numbers which can fuel stereotypes. 

BC: What is the cause for these misrepresentations?

EP: When we’re talking about shaping policy, we want information about the here and now. People don’t realize that simple questions about how many children women have are actually very difficult to answer, because you only know how many children women have once they stop having children—typically around age 45. So estimates of current fertility levels among women of reproductive age get computed through sophisticated demographic methods. Most of the time the models work. But when you encounter a phenomenon like a baby boom the estimates start to diverge from reality.

It’s even worse for immigrants. Immigrants tend to split their lives between sending countries and receiving countries. So take the question: How many children do immigrant women have? You can look at it in two different ways. There’s the perspective of how many kids will the woman have over her life—but that doesn’t really reflect what is important. The crucial question is how many children has she had in this country, because the people born in the U.S. are the ones that impact U.S. fertility. More importantly for our project, our current methods of estimating how many children women are having are thrown off when the timing of childbearing changes. I argue that because migration affects women’s birth timing, these methods tend to exaggerate immigrant women’s fertility. 

BC: What are the potential consequences if these disconnects are not repaired?

EP: The biggest potential consequence is simply bad population projections. One of the most important questions every society faces is: How many new residents does a country need to maintain positive population growth? If we over-estimate immigrant fertility, it throws off our estimates of the number of schools needed, the size of the labor force, the solvency of Social Security, and so on. It is critical to devise demographic methods that accurately reflect the interplay between migration and fertility, in order to better assess the future size and age structure of the U.S. population.

The scenario I’m describing affects all groups. It also presents a more nuanced understanding of immigrants’ contribution to the U.S. population. When Asians have children in the U.S., the child is more likely to have an immigrant parent than a U.S.-born parent. The same goes for Hispanics, Europeans, Canadians—it’s an immigrant thing. The domination of the race and ethnic perspective is an obstacle because behaviors that really come from a collective immigrant population acquire an ethnic or racial twist. With this grant we want to find new ways to bridge these gaps in methodology, and I think new research on these connections has the potential to impact the way we shape policy. It is especially important for the discussions surrounding immigration. Other things equal, a reduction in the number of immigrants that we receive, like the reduction we observed after the financial crisis, is also going to reduce our fertility rates, further contributing to population aging.