This paper deals with non-response bias, discussing a few approaches in this field. It is demonstrated that nonresponse bias as to voter turnout is lower in a survey on living conditions than in a purely political survey. In addition, auxiliary information from registrations is used to investigate non-response and its bias among ethnic groups. Response rates among ethnic minority groups are rather low, but there is no evidence that response rates are lower in lower social class areas. Unsurprisingly, correcting for limited socio-economic deviations.