Throwing a bit more into the “numbers game” as it pertains to whether folks actually attend church (either Protestant or Catholic) even as often as they say they do
religion-online.org/showarticle.asp?title=237
religioustolerance.org/rel_rate.htm
As to Catholics specifically, from a Catholic source
pncea.org/faq/statistics.asp
*Approximately 21,000,000 of the unchurched in America are inactive Catholics. This number is based on The American Religious Identification Survey, 2001 by Barry A. Kosmin, Egon Mayer, and Ariela Keysar from the Graduate Center of the City University of New York. The study provides one answer about the number of inactive Catholics. The authors found that of the Catholics responding, 59% belonged to a parish, and 41% did not. Drawing on U.S. Census information, the authors determined that 24.5% of the U.S. Catholic adult population in 2001, or 50,873,000 persons, were 18 or older. Of these, 41% or 20,858,000 were not members of a parish. Most of these 20,858,000 people are inactive Catholics…
Weekly Mass attendance has declined from about 75 percent in the 1950s to about 34 percent in 2005, according to Dr. Mary Gautier of CARA. The 34 percent figure is derived from phone surveys of 875 lay Catholics in 2005 by the Gallup Organization. The same study also found that 32 percent of baptized Catholics are not registered in a parish. Dr. Gautier reports that baptized Catholics who are registered in a parish (68 percent) are much more likely to participate in Church activities and to be satisfied with their Church, their parish, and their pastor.
These findings are reported in “American Catholics from John Paul II to Benedict XVI” by William V. D’Antonio, Dean Hoge, James Davidson, and Mary Gautier, The National Catholic Reporter, September 30, 2005. *