A perennial topic in industrial economics is collusion. Kwoka and Ravenscraft (1986) developed a model to measure the collusiveness of conjectures across industries as a function of intra-industry rivalry among leading firms. But extensive literature suggests that the degree of collusion may also depend upon underlying market characteristics. We modify the Kwoka and Ravenscraft model to account for this. Our results suggest that underlying market characteristics do matter. Intra-industry rivalry and conjectures vary with the level and stability of concentration, and to a lesser degree with product homogeneity.