I can tell you that Catholics have declined in terms of their share of the population in New York, as have Jews, while the non-religious have grown.
Of course, where I am writing these words (Washington State) the non-religious are at 28%, the largest "denomination" in the state and the highest proportion of non-religious in the world.
Methinks the Catholic Church growth in strongest in the South and the West, while declining (in terms of percentage of the population) in places like New York, Mass, and (possibly) New Jersey.
Bingo.
The Catholic parishes I attended in Minnesota and Wisconsin were dying...as were the schools. In North Carolina (where I lived six years ago) and here in San Antonio, we have booming standing-room-only Mass attendance and rapidly expanding Catholic schools.
Take the gun AND the cannolis and come on back!
Don't you believe it. I'm in the process of "crossing the Tiber", and at the Tacoma "Rite of Election", there were upwards of 500 converts at this one rite for just this year.