The population of the first three waves of the lidA study consists of participants born in 1959 or 1965 who were in employment (subject to social security contributions) on 31st December 2009. The participants from these cohorts are repeatedly interviewed at intervals of three or four years. Since the fourth wave it consists of further participants born in 1959, 1965 and 1971 who were in employment (subject to social security contributions) on 31st December 2019.
In the first wave in 2011 6.585, in the second wave (2014) 4.244, in the third wave (2018) 3.586 employees and in the fourth wave (2022/23) 8.884 employees were interviewed. The sample is representative for the German working same age population. A “sequential cohort design” was chosen for the study. This makes it possible to analyse whether the differences between the age groups arise due to age-related changes, different generations or whether they are a result of the societal change.