1. Broad description
For its social sample surveys Statistics Netherlands (Centraal Bureau voor de Statistiek, or CBS) releases about ten standard microdata files each year. The microdata are protected against disclosure but not to the last detail. The remaining risk is dealt with by a contract (or license). The microdata are available to legitimate researchers. They are released on tape or on disk, usually in the SPSS format.
2. Why is it good practice?
The community of social researchers is quite large. By releasing standard microdata files from its social sample surveys CBS serves this community. A basic acquaintance with SPSS is widespread among them.
Research on these files:
- reduces expenditure of taxpayers' money on data collection efforts;
- reduces response burden;
- provides researchers with readily available microdata;
- turns CBS files and corresponding definitions into a de facto standard;
- provides end users within the policy domain with high-quality information within a short turnaround time.
Social sample survey microdata are relatively easy to protect against disclosure.
Two of the national 'planning offices', or independent government research institutes (SCP and CPB) and some five university faculties have a full subscription to these licensed microdata files. In addition over 70 files are released to individual institutes and researchers.
3. Target audience
Microdata are released under a contract or license to legitimate researchers only. Section 41 of the law mentions the researchers that are qualified. Amongst them are universities and other research institutes with a legal foundation, but also Eurostat and NSOs within the EU. A residual category of applicants must be formally admitted by the Central Commission for Statistics (CCS), the supervisory body for CBS. The CCS has set its own selection criteria and procedures, in which a focus on statistical (aggregate) research, independence from administrative authorities, and the intention to share results in the public domain are predominant. The CCS has no objection in principle against admitting non-EU universities, for example. A commercial bank or a journalist would not be eligible, however.
4. Detailed description
Microdata files are released, nowadays usually on CD-ROM, to interested researchers that are qualified according to the law or to the CCS. The files are compiled and documented from the social sample surveys carried out by CBS. Of course, they do not contain formal identifiers or matching numbers. Other identifying variables are collapsed or protected in other ways. The sampling factor (1% for the Continuous Labour Force Survey being the maximum) by itself protects respondents.
5. Supporting legislation
Providing microdata to researchers is legally defined as an exception to the general obligation of statistical confidentiality. The general obligation reads as section 37:
- "1. The data received by the director general in connection with the performance of his duties to implement this act shall be used solely for statistical purposes.
- 2. The data referred to in the first subsection shall not be provided to any persons other than those charged with carrying out the duties of the CBS.
- 3. The data referred to in the first subsection shall only be published in such a way that no recognisable data can be derived from them about an individual person, household, company or institution, unless, in the case of data relating to a company or institution, there are good reasons to assume that the company or institution concerned will not have any objections to the publication".
The microdata release policy is supported by section 41:
- "1. Contrary to the provisions of Section 37 the director general may, on request, provide or grant access to a set of data to a department, organization or institution as referred to in the second subsection for the purposes of statistical or academic research where appropriate measures have been taken to prevent identification of individual persons, households, companies or institutions from those data.
- 2. A set of data as referred to in the first subsection may be provided to or made accessible to:
- a. a university, within the meaning of the Higher Education and Research Act;
- b. an organization or institution for academic research established by law;
- c. planning offices established by or by virtue of the law;
- d. the Community statistical agency and national statistical agencies of the member states of the European Union;
- e. research departments of ministries and other departments, organizations and institutions, in so far as the CCS has given its consent.
The importance of statistical confidentiality is apparent in section 42:
"The director general shall only grant a request as referred to in Section 41 if the director general considers that the applicant has taken adequate measures to prevent the set of data being used for purposes other than statistical or academic research."
The remaining risk of disclosure (considering the adequate measures mentioned in section 42) is dealt with by a contract or license. The contract is signed by the institute that has requested access to the microdata. An appendix to the contract is a confidentiality statement to be signed by each individual researcher with access to the data. There is no legal punishment or fine in the case of a transgression of legal or contractual obligations of confidentiality.
The research community itself has drafted, and agreed upon, codes of conduct for the social and epidemiological sciences. These codes have been accepted by the national privacy authority CBP. They may be interpreted as a sign of awareness on the side of researchers of ethical and legal problems of privacy and confidentiality. One of these codes installs a commission of appeal for respondents, on which a staff member of CBS serves.
Apart from supporting legislation there has been since 1994 a long-term contract with the Netherlands National Science Foundation (NWO). As a broker, it couples data providers, first and foremost CBS, and data users, primarily (but not exclusively) with a focus on the universities. Under this long-term contract, CBS obliges itself to make available at least eight social sample survey microdata files each year. NWO pays £450,000 per annum. Concrete users of microdata pay an additional small fee (varying from £1,000 to £5,000 depending on the size of the file, with a discount for older files, as well as for the full package for a whole year). NWO also organises publicity, user consultation days (on specific files or themes), and an independent formal evaluation every four years.
The researcher can process and analyse the microdata at his own computer, at his own time, with his own familiar and specialised software.
From the statistician's perspective an initial investment is needed for preparing and documenting the microdata file. But from then onwards, efforts can be quite minimal. The more microdata are used, the more value is added for society at large and for research in particular. Furthermore, the data quality and documentation is enhanced by feedback from intensive use.
From the researcher's perspective the microdata do not always contain sufficient detail. In some cases microdata are even deemed too sensitive to be allowed to leave the statistical office at all. For example, microdata from businesses, fiscal income statistics and causes of death statistics are not permitted to leave the office, which is an extreme example of collapsing the microdata.
Because of the lack of formal identifiers and the collapsing of some of the background variables, the microdata can not flexibly be expanded with new variables.
Some of the contractual conditions (CBS may want to screen draft publications or to inspect the ICT facilities on which the researchers have access to their data) are sometimes interpreted as 'organised distrust' if not outright 'strangulation' by CBS of research.
Some statistical staff consider it a threat that others use 'their' microdata and publish results that should have been on the official statistical programme.
30 Aug 2013