The last traditional population census in the Netherlands dates from 1971. Since then the willingness of citizens to participate in a census started to decline because of privacy considerations. Census information is still necessary for policy and research purposes. An alternative for the Census Programme 2001 was found in the Virtual Census. The advantages are its low response burden on the population and considerably lower costs. The Virtual Census 2001 uses the Social Statistical Database (SSD) as its source. The SSD contains a huge amount of data on demographic and socioeconomic issues. It is constructed by micro-linking several administrative registers and household sample surveys. A micro-integration process ensures coherence, consistency and completeness of the SSD-data. With a new method of repeated weighting, consistency can be achieved between register counts and sample survey estimates on an aggregated level.