2.2 Data, measures and descriptives 2.2.1 Data This chapter uses longitudinal data from the 1970 British Cohort Study (BCS70), which tracks around 18,000 individuals born in England, Scotland, and Wales during one week in April 1970. Since birth, there have been nine study sweeps, starting in 1975 at age five and ending most recently in 2021 at age 51. The data cover topics such as education, health, and social development and, essential for our study, include information on early language and math skills and life satisfaction measures across all sweeps. The longitudinal nature of the data allows us to examine long-term associations between early skills and life satisfaction. Additionally, all individuals in the sample are of the same age, eliminating age-related variability, and share similar historical and cultural contexts, moving through life stages simultaneously. 2.2.2 Measures Skill variables at age 10 We assess reading and math skills by two achievement tests taken in the sweep in 1980: the Shortened Edinburgh Reading Test and the Friendly Maths Test.1 All cohort members were ten years old at the time of these tests. We standardize the achievement test scores to a mean of zero and standard deviation of one to increase comparability among tests. 1Table A.3 contains a short description of these tests. 19
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