I recently put a comment on Carries blog "But These are Written". She attacks the notion of Catholic unity by presenting a survey that claims that there are large percentages of Catholics that don't believe in the Virgin Mary or attend Mass or believe in the True Presence.
But one thing these surveys did show, was as the people got more mature, they believed more. Now, perhaps I was wrong in saying that we are resolute in our faith.
No, I was not wrong, there are core dogmas of Catholic belief. If you reject any of these, then I don't care what you call yourself or what church you attend on Sunday, you are not Catholic. For anyone not sure, read Dr. Ott's list: http://jloughnan.tripod.com/dogma.htm
So, through around your surveys all you want, deny the true presence or virgin birth or the immaculate conception, and you are not Catholic.