The Transcription Factor Targets  ontology contains targets of transcription factors from ChIP-chip experiments. The sets were collected by Ron Shamir's group from the 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 Transcription Factor Targets statistics are available here.
GREAT v1.2 Transcription Factor Targets statistics are available here.
Linhart, C., Halperin, Y., Shamir, R. Transcription factor and microRNA motif discovery: the Amadeus platform and a compendium of metazoan target sets. Genome Res. 2008 Jul; 18(7):1180-9.