The 2011 Poland Population and Housing Census was the first since the country's accession to the European Union, and was conducted from April to June. A mixed methods approach was used for taking the census, where data was collected both through administrative sources and through surveying of the population, primarily in order to reduce the costs and level of bias in the final results. The survey portion of the enumeration process was completed via self-administered electronic questionnaires of a nationally representative 20% sample of households. Topics included in the forms were demographics, economic activity, migration, nationality, religion, and household characteristics. Over 2,744,000 of 13.5 million households were sampled. The total population in Poland for 2011 was enumerated at 38,538,000.