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Over the last twenty years, one of the most stunning changes to the American social landscape has been the dramatic rise in the percentage of Americans who report having no religious affiliation—the group that has come to be known as the “nones.” Today, 20 percent of Americans disclaim a religious affiliation,and among millennials, it is over 30 percent. At the same time, there has been a growing debate over whether the secularization of society will lead to a decrease in charitable giving, with secularists—whether they consider themselves atheists, agnostics, or humanists—tending to argue that fewer religious Americans will simply mean fewer contributions to pay for churches and synagogues that fewer Americans are attending anyway.

Not exactly. A new report by Jumpstart and the Indiana University Lilly Family School of Philanthropy details the many ways that religion and the charitable sector are intertwined. Based on a major national survey, this report finds that three-quarters of all household charitable giving goes to organizations that have religious ties. These span the range from large organizations like the Salvation Army (which, many Americans do not realize, is actually a church) to small soup kitchens run out of church basements.

(READ: Empty Pews: Everyone is Misreading the New Numbers of Religiously ‘Unaffiliated’)

Not only do Americans give generously to charities with religious affiliations, but the most religious Americans are also the most charitable. In our book American Grace: How Religion Divides and Unites Us, Robert Putnam and I show that there is a strong connection between being religious and being charitable. Not surprisingly, the most highly religious Americans contribute their time and treasure to religious causes. But they also give to secular causes—at a higher rate than do the most secular Americans.

Having found that religion and charity go hand-in-hand, Robert Putnam and I sought to understand why. The answer might surprise you. We initially thought that religious beliefs must foster a sense of charity—whether inspiration from biblical stories like the Good Samaritan or, perhaps, a fear of God’s judgment for not acting charitably. However, we could find no evidence linking people’s theological beliefs and their rate of giving—which also helps to explain why the “religion effect” varies little across different religions. The rates for charitable giving according to the Jumpstart survey are: 61 percent of Black Protestants; 64 % of Evangelical Protestants; 67 % of Mainline Protestants, 68 % of Roman Catholics, and 76 % of Jews. By contrast, only 46 % of the not religiously affiliated made any charitable giving.

Rather than religious beliefs, we found that the “secret ingredient” for charitable giving among religious Americans is the social networks formed within religious congregations. The more friends someone has within a religious congregation, the more likely that person is to give time, money, or both, to charitable causes. In fact, even non-religious people who have friends within a religious congregation (typically, because their spouse is a believer) are highly charitable—more so than strong believers who have few social ties within a congregation.

(MORE: The Selfish Reasons Behind Why We Give)

Our findings thus suggest that if secular organizations could replicate the sort of tight, interlocking friendship networks found within religious organizations, they too would spur a comparable level of charitable giving. At least some secularists have tried to do exactly this, by creating “atheist churches” that have the trappings of a religious congregation—weekly services, communal singing, and even a coffee hour—but minus the religious content.

The jury is still out on whether such religion-less congregations can keep people coming and, if so, whether the social networks formed within an avowedly secular group can have the same effect on charitable giving. In other words, can an “unchurch” replicate what churches do? Or does the boost to charity found within religious congregations require religion? Until recently, there was no way to tell. However, should unchurches prove to be more than a fleeting fad, we might soon have an answer.

David E. Campbell is the author of American Grace: How Religion Divides and Unites Us with Robert D. Putnam. He is the director of the Rooney Center for the Study of American Democracy and a professor of political science at University of Notre Dame. The views expressed are solely his own.