This study introduces a graphical methodology to the analysis of competitive balance in sports, which is prospective in nature and captures more subtleties than commonly-used retrospective measures. Thus, this study examines the evolution of competitive balance in Major League Soccer from 2004 to 2015, including the potential role played by certain league policies. For this purpose, we use prospective measures, based on probabilities that are extracted from betting odds (ex-ante) and on retrospective indicators (ex-post). The results differ slightly when analyzing competitive balance and predicting attendance. However, the graphical measures provide additional practical information about the characteristics of competitive balance.