[ElkGroveDan]

As we all know, these surveys never question how often the Catholic attends Mass.

Believe me, who call themselves Catholic and who are adherents to the true Catholic Faith are vastly different groups of people. As an example someone I knew lonnnng ago told me she was Catholic but argued that the Holy Eucharist was a symbol of Christ and nothing more. I recently connected with her on Facebook after many years and she is still listing herself as Catholic (and probably telling survey-takers she's Catholic as well).

[who_would_fardels_bear]

Maybe she’s Catholic spiritually but not religiously.

[TopQuark]

"As we all know, these surveys never question how often the Catholic attends Mass."

If you assume that true Catholics attend Mass regularly, then the poll tells you indirectly how many self-identified Catholics do so.