Evolution of the Initially Recruited SHARE Panel Sample Over the First Six Waves
Attrition is a frequently observed phenomenon in panel studies. The loss of panel members over time can hamper the analysis of panel survey data. Based on data from the Survey of Health, Ageing and Retirement in Europe (SHARE), this study investigates changes in the composition of the initially recruited first-wave sample in a multi-national face-to-face panel survey of an older population over waves. By inspecting retention rates and R-indicators, we found that, despite declining retention rates, the composition of the initially recruited panel sample in Wave 1 remained stable after the second wave. Thus, after the second wave there is no further large decline in representativeness with regard to the first wave sample. Changes in the composition of the sample after the second wave over time were due mainly to mortality related attrition. Non-mortality-related attrition had a slight effect on the changes in sample composition with regard to birth in survey country, area of residence, education, and social activities. Our study encourages researchers to investigate further the impact of mortality- and non-mortality-related attrition in multi-national surveys of older populations.