The surprise resignation of Pope Benedict XVI comes as the Catholic Church grapples with demographic changes and social forces that have profound implications for the church's identity - changes that will weigh heavily on the church's leadership as it selects its new leader.

In 1910, two thirds of the world's Catholics were in Europe. Today that figure is just 24 percent. "There's been such dramatic growth in places like Asia and Latin America and Africa," said Alan Cooperman, associate director for research at the Pew Research Center's Forum on Religion & Public Life. Nearly 40 percent of the world's roughly 1.1 billion Catholics now live in Latin America; another 16 percent live in sub-Saharan Africa, 12 percent in the Asia Pacific region, and 8 percent live in North America. (Catholics make up about 16 percent of the global population.)

At first glance, the Catholic Church appears to be healthy in the United States: According to data from the National Opinion Research Center, the percentage of Americans who consider themselves Catholic has held steady since 1972 at around 25.5 percent. But that finding masks the fact that many Americans have left the faith, as part of what appears to be a growing movement away from organized religion. In a broad 2007 survey, Pew found that "one-third of the survey respondents who say they were raised Catholic no longer describe themselves as Catholic." (Cooperman notes that roughly one in 10 Americas identify as former Catholics.) One major reason that the Catholic population in America has held steady is that the nation's Latino population has exploded, and 58 percent of Latinos identify as Catholic. By some estimates, 80 percent of the America Catholic population will be Latino by 2050, according to Baylor University history professor Philip Jenkins, who studies global Christianity.

The diverging fortunes of the church can be seen in countless ways. The sexual abuse scandals that cast a shadow over the church in the United States and Europe have not exploded in the same way in other regions. While the church struggles to recruit priests in America, people are entering the priesthood in large numbers in Africa; "the biggest problem is knowing what to do with all these priests," said Jenkins. And while the church has been criticized in the West for its stance on gay rights and women's health, it has not faced the same criticisms in much of the rest of the world.

Thomas Groome, chair of the department of religious education and pastoral ministry at Boston College, expressed hope that the church would not give up on the United States and Europe even as it "rejoices in the great growth of the church in the southern hemisphere."

"The southern hemisphere is culturally a different place, and it's a more traditional culture, but let's hope [the church] can make its way in a postmodern culture," said Groome.