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Problems in the family: Controlling for age, period or cohort in sibling comparison designs

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posted on 18.02.2021, 19:37 by Ben Wilson, Maarten J. Bijlsma, Siddartha Aradhya, Alice Goisis
The sibling comparison design is increasingly used across the social sciences as a means of controlling for observed and unobserved confounding, but this design is not without its methodological challenges. One challenge is to control for age, period or cohort when studying exposures that are measured in units of time. In such cases, variation between siblings in the exposure is typically collinear with variation in age, period or cohort – which makes controlling for these factors highly problematic. We address this challenge by showing how it is possible to control for cohort (or age or period) and obtain unbiased estimates of the effect of an exposure that is measured in units of time, albeit given certain assumptions. Using a simulation study that compares a series of estimators, we show that bias can be minimised by including a group who are discordant on age, period or cohort but concordant on the exposure.


the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme, Grant agreements No. 948727 (REFU-GEN) and No. 803959 (MARTE)

the Swedish Research Council (Vetenskapsrådet) via project 2017-01021

the Swedish Foundation for Humanities and Social Sciences (Riksbankens Jubileumsfond, RJ) grant registration number M18-0214:1

the Swedish Research Council for Health, Working life and Welfare (FORTE) grant numbers: 2016-07105, 2016-07115, 2018-00310 and 2019-00603

the project CRITEVENTS (financially supported by the NORFACE Joint Research Programme on Dynamics of Inequality Across the Life-course, which is co-funded by the European Commission through Horizon 2020 under grant agreement No 724363)




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Problems in the family: Controlling for age, period or cohort in sibling comparison designs

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310 Sociologiska institutionen | Department of Sociology