Religion is not a consumer product but, let's face it, many Americans "shop" for a religion when they reach adulthood or at other times. Viewed in that light, Catholicism is far and away the top choice for religious Americans.
As Pope Francis makes his first visit to the U.S., Catholics account for about 23% of the American population, a figure that has held remarkably steady for the 66 years that Gallup has been asking Americans about their religious affiliation.
One remarkable aspect of this relatively stable trend is that during the same period, the percentage of Americans who have no formal religious identity has increased from roughly 1% to about 20% today. The rise in those with no religion has been accompanied by a decline in the percentages of Protestants and other non-Catholic Christians, the ranks of which have fallen from as high as 70% of the population, down to about 50% today.
Catholics have been able to hold their own -- percentage-wise -- even as the unaffiliated percentage has risen significantly.
These results are based on Gallup's traditional "stand-alone" polls dating back to 1948. Religious identification is also measured as part of Gallup Daily tracking, and interviews with more than 170,000 individuals in 2014 showed a similar 23.9% of national adults interviewed identified as Catholic.
One of the explanations for the stable representation of Catholics in the adult population over time is the increasing percentage of Hispanics in the U.S. population, coupled with the fact that the majority of Hispanics identify as Catholic.
In Gallup's 2014 tracking data, 32% of Catholics identified as Hispanic, more than double the representation of Hispanics in the U.S. adult population. Sixty-one percent of Catholics are white, while 3% are black -- much lower than the black representation among Protestants.
No political preference
While in Washington, Pope Francis will meet with Democratic President Barack Obama and will make a speech before a joint session of the Republican-controlled Congress. This bipartisanship fits nicely with the party identification of Catholics in the U.S., which is remarkably similar to what is found in the overall population.
In 2014, 40% of both Catholics and non-Catholics identified as or leaned Republican, while 43% of both groups identified as or leaned Democratic.
This is a different situation from that of other religious groups, whose partisan identification tends to skew in one direction or the other. For example, 47% of Protestants and 71% of Mormons identify as or lean toward the Republican Party, well above the overall 40% of the population who are Republican. On the other hand, 61% of Jews identify with or lean toward the Democratic Party.
All of this explains why Catholics have been a key swing group in recent presidential elections, much more so than other religious groups. The tendency for Catholics to mirror the overall population from a partisan perspective is a shift from the past, when Catholics tended to skew significantly more Democratic in their partisan and voting behavior.
These data statistics are available in Gallup Analytics.