Conditioning Effects in Panel Studies. Systematic Review and Meta-Analysis for Sensitive Items

Panel data are indispensable for investigating causal relationships and answering longitudinal questions. However, it is controversial how the repeated survey of panel participants affects the quality of panel data. The expected learning effect of repeated participation is called panel conditioning and can have both positive and negative consequences for the validity of panel data. Sensitive items in particular are expected to have an impact on the social desirability of the information provided. The available evidence on conditioning effects for sensitive questions suggests different effects depending on the type of question and has so far only been processed in the form of narrative reviews. In the present meta-analysis. conditioning effects are examined on the basis of the available experimental evidence (154 effect strengths from 19 reports), depending on the type of question, as welt as the frequency and intervals between surveys (dosage effects). Standardized mean differences between experienced and fresh participants are analyzed by multi-level meta-regressions. The effects of previous surveys on the response behaviour in subsequent waves are only minor. At present, it can therefore be assumed that the quality of panel data is not influenced to a relevant extent by conditioning effects. Limits of the present meta-analysis and relevant research gaps are discussed.