Disclosure Risk for Tabular Data

In this chapter we consider the assessment of disclosure risk for tabular data. Disclosure risk may be defined either for the whole table or separately for each cell into which the table is organized. We shall sometimes use the term sensitivity as an alternative term for the disclosure risk of a table or cell. We suppose that a threshold may be specified as the maximum value below which the disclosure risk is deemed acceptable. Disclosure risk exceeding the threshold will call for the use of some form of SDC technique. For a measure of disclosure risk defined at the table level, we say that the table is sensitive if the disclosure risk of the table exceeds the given threshold. For a measure of disclosure risk defined at the cell level, we similarly say that a cell is sensitive if its disclosure risk is greater than the given threshold. In this book we restrict ourselves to measures of disclosure risk defined at the cell level. The objective of disclosure risk assessment will then be to determine which cells of a table are sensitive. We assume that a table containing sensitive cells may not be published. Having identified which cells are sensitive, the next step will be to treat these cells with an SDC technique such as cell suppression. This will be discussed in Chapters 8 and 9.