We are presenting a paper at the European Survey Research Association (ESRA) conference in Reykjavik in July 2015. Our paper ‘Using geocoded auxiliary data to predict nonresponse in address-based samples: Are household- level commercial data any better than aggregate-level census data?‘  looks at using auxiliary data to predict nonresponse in social surveys and compares the usefulness of household level commercial data and aggregate level census data. We are trying to answer the question, is it worth spending money on commercial data when you could get census data for free? We are presenting in the morning of Wednesday 15^th July as part of the ‘Enhancing survey data with geocoded auxiliary data 1’ session. The full conference programme can be accessed here.