An empirical evaluation of PRAM

PRAM (Post Randomization Method) is a disclosure control method for microdata. In 1997 it was introduced in Kooiman et al. (1997) and discussed more extensively in Gouweleeuw et al. (1998), but PRAM has not yet been applied extensively by statistical agencies. This is partly due to the fact that, even though some theoretical results exist, little practical knowledge is available on the effect of PRAM on disclosure control as well as on the loss of information it induces. In this paper, we will try to make up for this lack of knowledge, by supplying some empirical information on the behaviour of PRAM. To be able to achieve this, some basic measures for loss of information and disclosure risk will be introduced. PRAM will be applied to one specific microdata file of over 6 million records, using several models in applying the procedure.