The Human Phenotype ontology  contains data about human genotype - phenotype associations initially developed using information from Online Mendelian Inheritance in Man (OMIM) and now incorporating additional data from the medical literature.
Statistics can now be found in the footers of each table in the GREAT web output.
All ontology data was downloaded and built between Oct 14, 2011 and Feb 18, 2012.
GREAT v1.8 Human Phenotype statistics are available here.
Robinson, P.N. and Mundlos, S. The Human Phenotype Ontology, Clin. Genet. 2010 77:525-534