In this paper, we interpret the shadow economy (SE) as encompassing all forms of economic activities, which are not reflected in the official statistics (Lacko, 1998, Schneider, 2000). This definition includes all activities which generate added value that are in the "statistical underground", (nonresponding, non-registering, or not surveyed enterprises), the "economic underground" (underreporting or unregistered enterprises), the informal sector, or the illegal sector.