Statistics Netherlands collects and publishes data to provide insights into various social topics. To offer a coherent and current picture of living in the Netherlands, one of the societal challenges from the CBS multi-year plan, CBS started an innovation project in 2017 together with the Ministry of the Interior. Nine years later, the innovation project is nearly complete and the Woonbase has grown into a rich and reliable information source for researchers, policymakers, and government agencies. By combining different data sources, the Woonbase offers new insights into the Dutch housing market.

Unanswered questions

Due to changes and challenges in the housing market, there was a desire to make as much unambiguous information on this topic available as possible, says Jesper van Thor, project leader of WoON innovation at CBS. Before the establishment of the Woonbase, we mainly depended on various more or less separate registrations and the WoON survey for data about housing. This survey consists of a triennial questionnaire distributed to part of the population. Although important information, such as satisfaction with the home and moving wishes, can only be obtained through such surveys, the information need is often broader. With the Woonbase, it is now possible to publish figures for specific target groups and at a low regional level, thus providing better insight into local developments.

To meet this broad information need, the Woonbase was compiled using information available in existing registers. These already contain a lot of information. Van Thor: By combining various sources such as the Basic Registration of Addresses and Buildings (BAG) and the Basic Registration of Persons (BRP), we are able to provide a complete and recent picture of how many people live at an address, what the monthly housing costs are, and under which energy label the house falls. By combining these existing data, CBS can offer more insight without asking extra questions in the WoON survey. We will continue to use these, among other things, to collect missing information in the registers, such as information about house sharers.

New research opportunities

The combination of various data sources in the Woonbase opens new research possibilities. One of the many researchers using the Woonbase is Matthijs Korevaar, assistant professor at the Erasmus School of Economics. According to him, the database has created many new research opportunities. Especially the financial-economic component added in recent years provides new insights. For example, Korevaar researched how much landlords earn from renting out homes in the private sector. Something that was not possible before the realization of the Woonbase. It appeared that private landlords earn the most from the lowest quality homes. Based on these results, we also conducted research for the ministry on the predicted effects of the new rental law by former housing minister Hugo de Jonge. This research report was also sent to the House of Representatives.

User day

To serve users of the Woonbase well and further improve the data source, CBS organizes an annual user day. We invite various housing market researchers to inform them about important developments around the Woonbase and hear their experiences with its use, says Van Thor. In this way, we have already been able to make several optimizations and additions. Besides, it is also very nice and educational to hear how users use the Woonbase data in their own work!

Bigger and more successful

The ministry also sees the value of the Woonbase. Katja Chkalova, coordinator basic research at the Ministry of Housing and Spatial Planning (formerly BZK) and collaboration partner at the Woonbase, is satisfied with the results achieved so far. It has become bigger and more successful than we expected. Almost all research institutions work with it. It makes life much easier for many researchers, she says enthusiastically.

Five months earlier

Although the development phase of the Woonbase is almost complete, there are still over thirty subprojects involving about seventy CBS employees. For example, we want to better map the living situation of certain groups who are not well represented in registers and are also difficult to reach via the survey, says Van Thor. Think of students living together with six or seven people in one building. Do they see themselves as one household? Do they have a joint account or is there a main tenant who pays the rent every month? There is also a continuous effort to make the figures available faster. We have recently made progress in this. The figures for the most recent Woonbase year were now available five months earlier, says Van Thor.

Treasure trove

In the final phase of the project, which runs until and including 2027, the focus is also on further professionalizing the Woonbase. How do we ensure that the database is future-proof? How do we arrange maintenance? These are questions we can now focus on, says Chkalova. But also: how do we make Woonbase data accessible to more users? adds Van Thor. The protection of respondents privacy is always central. Only parties with an institutional authorization can work with Woonbase microdata under strict conditions. At the same time, Woonbase information at an aggregated level, for example via StatLine tables and news reports, is accessible to everyone, says the project leader. This way, a large audience can make use of this treasure trove of information.