Data Swapping for Protecting Census Tables

Abstract

The pre-tabular statistical disclosure control (SDC) method of data swapping is the preferred method for protecting Census tabular data in some National Statistical Institutes, including the United States and Great Britain. A pre-tabular SDC method has the advantage that it only needs to be carried out once on the microdata and all tables released (under the conditions of the output strategies, eg. fixed categories of variables, minimum cell size and population thresholds) are considered protected. In this paper, we propose a method for targeted data swapping. The method involves a probability proportional to size selection strategy of high risk households for data swapping. The selected households are then paired with other households having the same control variables. In addition, the distance between paired households is determined by the level of risk with respect to the geographical hierarchies. The strategy is compared to a random data swapping strategy in terms of the disclosure risk and data utility.