When we send advance letters to the sampled persons in a survey, we expect that the recipients will read them and, based on the information provided, will decide on their participation in the survey. Therefore, the letter ...

In this paper we show how one method of increasing the response rate, i.e. an extension of the fieldwork period, influences the structure of non-response and the differences between respondents and non-respondents. We used ...

In Poland, like in other countries, participation in surveys is declining over time. The growing non-response rates increase a risk of systematic bias of the results depending on the differences between non-respondents and ...