Cell Suppression as used to Protect Magnitude Data Tables
Massell, Paul B.
The most common data products released by the Economic Directorate of the Census Bureau are magnitude data tables. Common magnitude variables in these tables are ‘sales’ (aka ‘receipts’), and ‘number of employees’. In this method, an agency uses the p% rule for determining which cells reveal too much information about particular establishment or company value contributions to the cell. Such a cell is declared sensitive and is suppressed. However, since Census tables are typically additive, additional cells, called ‘secondary’ suppressions, must also be suppressed in additive to make it impossible for a table user to recovery the value of any sensitive cell. Using techniques from operations research, Census Bureau researchers developed methods for finding these secondary suppressions in a way that minimizes information loss from the table. Good software had been developed about 1990 for implementing cell suppression. We will discuss improvements to the method that have been implemented in the current version, such as better protection at the ‘company level’, handling of negative values, and improved processing of linked tables.