I'm looking to compare the read rate of an email newsletter with the read rate of another newsletter. However, many (not all) of the people who receive one newsletter also receive the other. What would be the best method to determine whether the proportions of people who read the newsletters are significantly different, given that there is a large overlap in the samples?
I know of McNemar's test, but that requires matched pairs of subjects. The newsletters' datasets are stored differently, so I unfortunately can't see whether an individual who has read one newsletter has also read the other.