On cartel detection and Moran’s I

Abstract

This paper explores the potential of using the Moran’s I statistic to detect complementary bidding on public contracts. The test is applied to data concerning the so-called Swedish asphalt cartel, which was discovered in 2001. Using information on submitted bids and procurement characteristics for both the cartel period (1995–2001) and the post-cartel period (2003–2009), the Moran’s I correctly predicts complementary bidding behavior for linear and quadratic specifications when such behavior is likely to exist, and rejects such behavior when it’s unlikely to be present. Remarkably, the Moran’s I also correctly indicates and rejects complementary bidding on the basis of information on the separate bids alone.