Younger siblings may indeed look up to their older kin — to the point that it influences where they go to college.

Using data from centralized school systems in three countries, a team of researchers that includes Princeton University economist Christopher Neilson finds causal evidence that social interactions greatly influence where students go to school.

Specifically, the researchers find that younger siblings are significantly more likely to apply and enroll in the same college and major as their older siblings.

The findings suggest that college access programs, like affirmative action, not only affect the higher education trajectories of their direct beneficiaries, but also the choices made by other members of their families.

“The choice of where to go to college and what major to study is one of the most complex and consequential decisions that an individual can make. But we find that random luck affecting an older siblings' college trajectory can lead to significant changes in the choices made by younger siblings. This causal evidence across three very different countries highlights the importance of family and peer networks in shaping crucial life decisions,” said study co-author Christopher Neilson, assistant professor of economics and public affairs at Princeton’s Woodrow Wilson School of Public and International Affairs.

Centralized admissions systems in Chile, Croatia, and Sweden provided a valuable setting for the research. In each of these systems, students applying to college are allocated to schools and majors only depending on their stated preferences and previous academic performance. These selection systems give rise to sharp admission cutoffs in all oversubscribed majors, where some students received their preferred placement based on random luck.

The researchers looked at students near the cut-off that receive their preferred placement and study whether and how their enrollment in a specific institution or major affects their younger sibling’s probability of applying and enrolling in the same program and institution.

They found that when an older sibling slightly above of the cutoff is able to enroll in their preferred major, the likelihood of their younger sibling applying to that same program increased between 1 and 4 percentage points. Further, students are between 10 and 16 percentage points more likely to apply to the college where their sibling is enrolled and between 4 and 9 percentage points more likely to enroll there.

The effects the researchers document are stronger when students resemble their older siblings in terms of gender and academic performance in high school, and when older siblings enroll and are successful in majors that, on average, have higher scoring peers, lower dropout rates, and higher earnings from graduates. Despite the differences that exist between Chile, Croatia, and Sweden, they found similar spillover magnitudes in all three countries.

The researchers explored several hypotheses for why younger siblings are significantly more likely to apply and enroll in the same college and major as their older siblings. They found little evidence that the decision is based in practicality (i.e. it’s easier to commute together), nor did they find evidence that it’s based on siblings wanting to attend school together.

“Though we can’t perfectly distinguish the exact mechanisms behind our results, we provide suggestive evidence consistent with the idea that the effect is driven by older siblings being a major source of information about a school’s quality and the type of experience young siblings can expect,” Neilson said.

Identifying these family spillovers has important policy implications. First, the findings could help to explain inequality in education uptake and trajectories across families and socioeconomic groups. Relatedly, the effects show how policies that change the pool of students admitted to specific programs and institutions, such as affirmative action, can have an indirect multiplier effect on members of the social network of their beneficiaries.

Finally, it is possible that students are making education decisions based on their older siblings’ choices because of incomplete information about other options. It is possible to improve the match of students and educational programs by providing that information.

The paper, “Causal evidence that social networks drive college decisions,” was posted as a working paper on DataSpace at Princeton University, a digital repository meant for both archiving and publicly disseminating digital data which are the result of research, academic, or administrative work performed by members of the Princeton community.

In addition to Neilson, co-authors include Adam Altmejd, Stockholm School of Economics; Andrés Barrios-Fernandez, Centre for Economics Performance (LSE) and VATT; Marin Drlje, Center for Economic Research and Graduate Education – Economics Institute; and Dejan Kovac, Princeton University.