The Bureau of Transportation Statistics’ Statistical Disclosure Limitation Method for Tabular Data: a Review

Overview The United States Department of Transportation’s Bureau of Transportation Statistics (BTS) is developing its confidentiality policy which is based on its legislative mandate (49 U.S.C. 111(i)) to protect individually identifiable information. Because the field of statistical disclosure limitation (SDL) research is still evolving, BTS wants to take advantage of the latest SDL research in updating its confidentiality policy and practices. To this end, BTS has undertaken research that seeks to develop a new method to limit disclosures in complex, multi-dimensional (up to five) tables that contain a hierarchical structure. This research will also offer a new way of protecting confidentiality while at the same time increasing access to data. In this paper we present a review of the literature of the current disclosure limitation methods for tabular data. We identify, describe, and classify the methods. We briefly describe BTS’ current methods of disclosure limitation and identify reasons for change and enhancement. Finally, we propose a new method for tabular data disclosure control and a research agenda that includes phases for developing and implementing the new method.