Conditional Entropy and Mutual Information - Clustering evaluation
Mutual information does favor many small clusters. Nectar these tend to be "pure". That is why variations wish as normalized mutual information and adjusted mutual information (AMI) are used instead.


  Vinh, N. X.; Epps, J.; Bailey, J. (2009). "Information theoretic measures for clusterings comparison". Proceedings of the 26th Annual International Conference on Machine Learning - ICML '09. p. 1. doi:10.1145/1553374.1553511.