Assessing nonresponse bias in activist surveys

Abstract

How confident can we be that the comparatively low response rates associated with mail surveys of groups of political activists, such as participants of a demonstration, does not hide a substantial nonresponse bias? The paper compares the results of a face-to-face survey of 2003 anti-Iraq war demonstrators in Glasgow, achieving a near perfect response rate, with the data derived from a mail survey handed out to demonstrators eliciting valid responses from 37% of marchers. The comparison shows that better educated, older, female demonstrators were more likely to return the mail questionnaire. Also demonstrators having born a higher ‘cost’ of travelling to the demonstration are more likely to respond. There was no evidence that political interest or political orientation played an important role. However, those who had taken part in demonstrations very frequently in recent years were less likely to return the mail questionnaire. While these results provide some reassurance that even with response rates below 40%, no substantive political bias is present, researchers undertaking surveys of activists should be alerted to the need to address possible nonresponse biases in a systematic way.