Most of the protestant losses are white mainline groups - people like the episcopalians, lutherans, presbyterians.
There’s no evidence of similar losses among White Catholics. If anything, at least in America, there are more white Catholics than before. :)
I believe you're right about Protestants, but your information is way off base regarding "white Catholics":
.... Catholics still account for just under a quarter of the population, as they have for many years. That's because the surge in Hispanic immigration has offset the steady decline of white Catholics. Roughly 2 in 3 Latino immigrants are Catholic, according to Luis Lugo, director of the Pew Forum. He also notes that Hispanic fertility rates are higher than those of white Americans, ensuring more Latino Catholic growth in the United States........Catholics are leaving the faith at four times the rate that newcomers are joining. "Religious change is not simply a function of retention; it's a function of recruitment. It's both sides of the ledger," explains the Pew Forum on Religion and Public Life's Greg Smith. "In no other religious groups we looked at did we see this high a ratio people leaving versus joining."
.... from the thread Does the American Catholic Church Have a Numbers Problem?
No other religion in the United States has lost more members to other faiths, or to no faith at all, than Catholicism, according to the new survey released by the Pew Forum on Religion and Public Life. The survey, conducted in 2007, found that 31 percent of Americans were raised Catholic, but less than 25 per cent of them still identify as Catholic. Roughly 10 percent of all Americans have strayed from Catholic roots, the study reported.....
.... from the thread Study: Catholics losing the faith
“found that 31 percent of Americans were raised Catholic, but less than 25 per cent of them still identify as Catholic”
Now compare that to the 62-52, or 20 percent losses for protestants.
Is it really true that it’s the Catholic church that’s suffering the highest losses? Really? That’s not what I’m seeing.
Whole denominations - the Episcopalians, Lutherans, Presbyterians, Methodists, are getting stomped? Why? Because they’ve abandoned what God teaches and have decided to go with the baby boomer ideals, “if it feels good, do it”.
The questions you should be asking is why is the Catholic church doing better with White people than Protestant churches are doing with White people?
Here’s a pretty good article from First things.