Example apparatus disclosed herein are to compare (i) ratios of program ratings to corresponding network ratings with (ii) a threshold to determine adjusted viewing data for respective sites during a monitoring interval, the program ratings and the corresponding network ratings determined for programs tuned on corresponding networks at the respective sites during the monitoring interval, the adjusted viewing data for a combination of a first program and a first site to represent an adjusted amount of time the first program was presented at the first site. Disclosed example apparatus are also to cluster the programs into program clusters based on distances between respective combinations of pairs of the programs, the distances based on the adjusted viewing data. Disclosed example apparatus are further to output information to identify the program clusters.