Response Rate and Nonresponse Bias - Impact of the Number of Contact Attempts on Data Quality in the European Social Survey

Increasing respondent contact problems and decreasing respondent willingness to cooperate have contributed to declining response rates in general population surveys, which has raised concerns of survey accuracy. To counteract nonresponse, several methods have been employed, including incentives, advanced letters, alternative survey modes for reluctant respondents, and increased field efforts to contact potential respondents. In particular, the number of contact attempts has been increased for many surveys. Even though more contact attempts increase survey costs, they are a reliable means for increasing response rates. However, the assumption that high response rates foster data quality and smaller nonresponse bias has been challenged. In this paper, we used contact data from the European Social Survey for Norway, Finland and Slovenia to see whether or not additional contact attempts resulting in a higher response rate can potentially reduce nonresponse bias.