Increased corporate, government and academic demand has prompted official statistics to release individual respondent data (microdata) in addition to the traditional tabular data. Microdata must be masked by a statistical disclosure control (SDC) method before being published, because otherwise the statistical confidentiality of respondents would be compromised. A novel application of watermarking is discussed in this paper which allows multilevel access to numerical microdata: depending on her clearance, the data user can remove more or less of the masking. Non-privileged users just see the published data, but as the clearance of a user increases she can get a data set which is closer and closer to the original one.
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