Bid-Rigging Cartels and Data. Screens. Variance Screens. Coefficient of Variation. Kurtosis. Cover-Bidding Screens. Percentage Difference. Skewness Statistic. Relative Difference. Alternative Relative Difference. Structural Screens. Number of Bidders. Contract Value. Descriptive Statistics. Empirical Analysis using Machine Learning. Lasso Regression. Ensemble Method. Empirical Results. Policy Implications. Data Requirements and Data Use. Generalization of Results.