One paper is written by Hayley Jang, Young Hoon Lee and Rodney Fort. It is published in Economic Inquiry. They note that "Quite often, competitive balance is measured by some version of the standard deviation of winning percentage or by the behaviour of winning percentage in the tails of its distribution. But again, nearly nothing is known about the distribution of winning percentages in the first place". They recommend analysis of the basic tests of the form of the distribution. A neat illustration is presented where they point out that the North American Leagues exhibit negative skew (longer left tail) whereas the European Leagues exhibit positive skew. Why is this important? The negative skew in North American Leagues suggests the imbalance is due to the weaker teams whereas in Europe the opposite is the case. There is some suggestions as to why this might be the case.
This first paper lends further support to the literature showing reduced competitive balance in European Soccer Leagues. A similar finding appears in the second paper.
The second paper is written by Francisco Triguero Ruiz and Antionio Avila-Cano. It is published in Applied Economics. The paper examines various measures of competitive balance and proposes an alternative measure. This alternative measure allows the calculation from ideal competitive balance in "distance" terms. As a result, it facilitates comparisons between competitions with different numbers of teams and games. Section II and III provide some technical comparison on measures. There is also a nice appendix providing calculations of various measures for the top European leagues for the last two decades.