Periodic Reporting for period 3 - SIBMOB (Social Class Mobility in Comparative Perspective: Bringing Siblings In)
Reporting period: 2024-02-01 to 2025-07-31
Why siblings? Well, they grow up in the same house, with the same parents and often in the same community. They even share some of their genes. But as anyone with a sibling knows, brothers and sisters can be very different. They might have different talents, interests, or ideas about life. They also vary in terms of gender, birth order, the friends they hang out with, or the schools they attend.
This is the key insight: SIBMOB uses these similarities and differences between siblings to measure how much your family background affects where you end up in life. Basically, if siblings from the same family often end up in similar social classes as adults, that suggests family background plays a big role. On the other hand, if siblings wind up in very different social classes, family influence might not be as strong as we thought.
To dig into this, SIBMOB uses new techniques to study siblings' social class positions as adults. We are pulling in data from more than 10 countries to explore whether family background holds more or less weight depending on where you are from. We are also looking into if the influence of family background has changed over the past 100 years.
In summary, SIBMOB aims to uncover how your family's status can shape your life. By looking at siblings who grew up in the same environment but took different paths, we are unlocking clues about the real power of family influence. The ultimate goal is to use this information to help governments create policies that ensure that everyone has a fair shot at success, no matter where they started in life.
Methods: We are pioneering new approaches to studying social mobility among siblings. We have developed specialized statistical software that can handle complex sibling data, now publicly available for the wider research community. In addition, we have introduced several novel statistical techniques that offer a more nuanced understanding of why siblings end up in similar or different social positions as adults. These contributions have been published in peer-reviewed international journals.
Data: We have built a large cross-national database combining information on siblings’ social class positions, upbringing, and parental background. The database integrates more than 20 datasets from 11 countries and covers over 400,000 siblings. We have also linked in country-level variables such as inequality and educational expenditure to allow richer contextual analysis. Our data construction process is fully documented, ensuring transparency and replicability. In addition, we fielded a comprehensive survey in Denmark of around 70,000 first cousins and their parents, collecting unique information on political attitudes.
Analyses: Drawing on our methodological and data advances, we have carried out the following studies:
(1) We investigated sibling social class mobility across ten industrialized countries. Findings reveal surprisingly little cross-country variation, with important theoretical implications.
(2) We examined how marital status and gender influence socio-economic similarities among siblings, using data from the United States and Denmark.
(3) We analyzed whether sibling similarities in occupation and income are due to the same or different family characteristics. Using data from Denmark and the United States, we found that both outcomes are shaped by largely the same family factors.
(4) We studied how family background affects income across different stages of the life course, finding a surprising life time stability in the influence of family background.
(5) We used Danish administrative data to assess how the financial returns to different college programs vary with family background and parents’ educational choices. For example, we examined whether siblings are more financially successful when they follow the same educational paths as their parents.
(6) We conducted the first comparative study of sibling similarities in income “instability” across Denmark, Germany, and the United States. We find that family background matters for exposure to volatility, but more so in the United States and Germany than in Denmark.
(7) We are examining how family background shapes political attitudes, including orientations towards political parties, and the extent to which these family influences overlap with those affecting educational attainment.
(8) We studied how older parents allocate time and resources among their children’s families, focusing on factors such as gender and education.
Collectively, these projects advance our understanding of how family background shapes social and economic mobility. They make important contributions to academic theory and have significant implications for policy debates on inequality and intergenerational transmission.
Our approach is multifaceted. Beyond simply crunching numbers, we are constructing a comprehensive framework to explore numerous factors that can affect one's social mobility. By the project's conclusion, we anticipate delivering a thorough, nuanced understanding of siblings' social class mobility. We aim to provide substantive evidence on how and why social mobility differs across countries and time. Additionally, we plan to present insights into tangential yet crucial questions, such as how marriage or education can act as catalysts for social mobility.
The implications of our findings are expected to be significant, not just for academic theories that seek to explain social mobility, but also for policy considerations aimed at enhancing equal opportunities in society. In essence, the SIBMOB project is set to offer invaluable contributions to our understanding of social mobility by creating a robust, interdisciplinary framework that goes beyond the current state of research.