The proportion of Catholics reporting strong religious affiliation declined by almost twenty percentage points over the last few decades, from 46 percent of Catholics in 1974 to 27 percent in 2012. Protestants reporting strong religious affiliation increased more than ten percentage points during the same period, from 43 percent to 54 percent....Strong Catholics have lost ground, both proportionally among Catholics and also in the entire population. As can be seen in the chart below, the proportion of strong Catholics in the overall U.S. population has declined about 40 percent from 1974, from twelve percent of the entire adult population to seven percent.... ....A trickle of high-profile converts cannot numerically offset the laity leaving Catholicism for other churches or no church at all, but their conversions—often made with some reference to perceived Catholic intellectual vibrancy—may reflect a strength in the Catholic Church not captured by the numerical measures....
....The implication of the Pew report seems to be status-quo holding for Protestantism: It is maintaining its core members while losing its more peripheral members (hence core members make up a greater proportion of Protestants, even though core members are not increasing numerically faster than population growth). The implication is more concerning for Catholics: Even though overall numbers are maintaining, core membership is declining.
Hispanics will continue as a group to make up for the loss of Anglo members in the U.S. Catholic Church.I've never met a immigrant from Mexico who was Catholic. They are either Evangelical, or Jehovah's Witness. Maybe some unaffiliated. People in the U.S. don't seem to realize, Mexico was founded by rabidly anti-Catholic people, with an explicitly anti-Catholic constitution. It was not even fully legalized to be a Catholic priest in Mexico until 1998.
From the article "The increase in the proportion of Protestants who report a strong religious identity may result not from an overall increase in the number of strong Protestants, but rather from a decline in the number of “weak” Protestants."
Thats it entirely. The mainline denominations are shrinking and it will only speed up in the next few years. Its less about doctrine and more about average age of members and the number of kids they have been having, or not having. A profile of the current age demographic of the largest protestant denominations is
available here.
Protestants are in open numeric decline as the graphs in the above article show, over the same period catholic numbers are steady as a % of population. The steady % number of Catholicism in the population is a sign of huge growth.
For the periods of the graph above
from ARDA... In 1974 Catholics numbered 48 million, in 2010, at least 68 million, an increase of 20 million. And that includes accounting for all those who left Catholicism during that period and now identify as other than Catholic.
In other words for the period of the graph above the Catholic numbers grew by the combined total of the Southern Baptists and the Presbyterian Church members.