The U.S. Religious Landscape Survey finds that more than one-in-four (27%) American adults who are married or living with a partner are in religiously mixed relationships. If people from different Protestant denominational families are included – for example, a marriage between a Methodist and a Lutheran – nearly four-in-ten (37%) couples are religiously mixed.

The survey, conducted by the Pew Research Center’s Forum on Religion & Public Life, finds that people who are unaffiliated with a particular religion are the most likely (65%) to have a spouse or partner with a different religious background. Buddhists (55%) also are likely to be married or living with a partner with a religious background different from their own.

In contrast, the individuals least likely to marry or live with a partner outside their faith include Hindus (only 10% are married to or live with someone of a different religion), Mormons (17%) and Catholics (22%).

Source: Pew Forum U.S. Religious Landscape Survey, conducted in 2007 and released in 2008. Based on respondents who say they are married and respondents who say they are living with a partner.

* Includes marriages and partnerships between people from different segments of the unaffiliated population (e.g., a marriage between an atheist and an agnostic).

** Includes marriages and partnerships between people from different Protestant denominational families (e.g., a marriage between a Methodist and a Lutheran).

Among all religiously mixed marriages and partnerships, the most common combinations are Protestant-Protestant, where each partner is from a different denominational family (25%); Protestant-Catholic (23%); and Protestant-Unaffiliated (20%).

Source: Pew Forum U.S. Religious Landscape Survey, conducted in 2007 and released in 2008.

* “Other faith” includes all respondents identifying as something other than Protestant, Catholic or unaffiliated.

** “Other mixed marriages” includes marriages and partnerships between people of different faiths within the “Other faith” group, as well as marriages and partnerships between people from different segments of the unaffiliated population (e.g., a marriage between an atheist and an agnostic).

Note: Numbers may not sum to 100 due to rounding.