Dear david. Thank you for visiting the KOSIS website. The Population and Housing Census includes the complete survey and the sample survey. As for the complete survey, the Register-based Population and Housing Census has been annually carried out by using administrative data since 2015, and a rolling census is not carried out. As for the sample survey, the Census is carried out every 5 years. As for survey methodology, at first, the Internet survey is applied. Afterwards, a face-to-face interviewing method is applied to non-respondents. In the 2005 Census, 0.9% of respondents used the Internet survey. And in the 2010 and 2015 Census, 47.9% and 48.6% of respondents used the Internet survey, respectively. Thank you.