A Caution on Sibling Comparisons in Studying Effects of the Rearing Environment

Abstract

Recent studies use family fixed effects to estimate the influence of parental characteristics on children, a practice we call the “discordant parenting design”. This approach is valid only if treatment effects are equal within and between families. This assumption is mostly not informed by relevant theory and, we argue, unlikely to hold in practice. In addition, within-family confounding, reverse causality, and selection into identification complicate the interpretation of these studies further. We discuss three applied examples—the effects of parenting, family income, and neighborhood context—and provide some general guidance. To avoid misinterpretation, researchers should have a strong grasp of the variance that enters into estimation, and not just the potential confounders that a given strategy is designed to deal with.

The association between childhood income and mental health: can sibling comparison designs help resolve this research question?

“…Such results were followed by the interpretation that the association between income and mental health observed in the full cohort might be fully explained by unmeasured confounders and is thus not consistent with a causal interpretation. 10 However, similar to other researchers, 6,[11][12][13] we believe caution should be made when using sibling comparison designs in such a setting. As family income is the same for all siblings at any given time, the sibling comparison design relies on imperfect overlap -i.e.…”

“…age differences -in the sibling life course. 11 Thus, such results must be interpreted considering further analyses.…”

The Taller the Ladder, the Tougher the Climb? : Essays on the Impact of Income Inequality on Intergenerational Mobility

“…Chetty et al (2014b) find that U.S relative mobility, as measured by the rank-rank slope, remains essentially unchanged. As does Lee and Solon (2009), also studying U.S. Engzell and Hällsten (2022) find a stable trend for men in Sweden, but decreasing mobility for women. However, this outcome is anticipated, as for older cohorts, mobility rates were inflated due to low labor force participation among women.…”

“…The permanent income hypothesis deals with the same issue, asserting that consumption and, ultimately, economic welfare are influenced by the permanent expectation of income rather than income in a specific year (Friedman, 1957). Consequently, fluctuations in income over a few years can be viewed as a form of measurement error (Mazumder, 2005;Torche, 2015;Engzell and Hällsten, 2022). This perspective is consistently applied throughout this dissertation, where lifetime income serves as a proxy for measuring both income inequality and for intergenerational income mobility.…”