Bid rigging cases have traditionally involved a large share of criminal cases filed by the antitrust agencies across the countries. Bid riggings are naked restraints of trade and perse illegal in violation of section one of Sherman Act. There were many indictments of firms in construction industry, school milk industry, electrical equipment industry, real estate, antiques and other auction markets. In spite of this trend, the empirical literature on collusion in auctions is not fully developed. This study shows how to systematically and statistically detect the presence of collusive bidding behavior in auctions and properly estimate damages to consumers or taxpayers. The antitrust agency can not easily obtain the solid evidence of bid rigging such as wiretaps, witness of whistle blowers, and so forth. Therefore, the detection of bid rigging is not an easy task. The antitrust agency needs to distinguish between collusive behavior and noncooperative behavior, both of which lead to supracompetitive profits since some statistical indicators generally associated with collusion may arise in an equilibrium of noncooperative game. The appropriate methods for the detection of explicit bid rigging and noncooperative tacit collusion require the detailed statistical analyses of strategic behaviors and market environments in addition to simple regression-based analysis. This paper illustrates the effects of limits of current legal enforcement in relation with collusion inference at the levels of Fair Trade Commission and Courts. This research strongly suggest that competition agency delete the unfair collusion inference code of Antitrust Law and adopt the actual inference based on solid circumstantial evidence. And Also, It provides that reasonable approach for the relevant refusal of collusion inference.

The accurate assessment of damages is a key issue in litigation involving a bid rigging. The assessment of damages is often a principal issue in litigation because the interests of plaintiff and defendant directly conflict. Primary objective of the plaintiff is usually to collect as much as possible and that of the dependant is to pay as little as possible. In order to recover antitrust damages, the plaintiff in a bid rigging case must be able to prove the amount of the price change suffered as a result of a conspiracy. Even if the proof of damages is obviously critical to plaintiffs and defendants alike, there are very few empirical studies on this subject. Three alternative techniques can be successfully used for preparing damage cases. The first is cost method approach looking at the relationship between winning bid and professional’s estimates of competitive bid on the basis of sketch cost data. The second is dummy variable approach estimating over the pooled sample of rigged and unrigged contracts with a dummy variable which is equal to one if the job is rigged and equal to zero if it is unrigged. The third is a forecasting approach using only unrigged bids as a control group to estimate the model and then plugging the data points for each rigged bid into estimated model. However, it should be noted that these estimates are poor substitutes for estimates based on reliable cost data. This study investigates the effect of the regulation change on the formation of cartel, antitrust damage suit, and the imposition of administrative fine. This study suggests that the government agency should asses the basic fine on the basis of proper damage estimation, not on the basis of the certain percentage of gross sales. This legal approach may help the consistency, the stability, and predictability of legal enforcement. This study also suggest that at the stage of active antitrust damage suit, the financial remedy rely on damage suit and the fine focus on administrative regulation reflecting dead weight loss and enforcement cost due to the collusion in oligopoly market. The punitive compensation system needs to be introduced restrictively in hard-core cartels.

Author hopes that this study may be a practical guidance to competition agency, consumers and government, lawyers, firms, and judges in regard with antitrust collusion cases and antitrust damage suits.