The United States is officially a secular nation; the First Amendment of the U.S. Constitution guarantees the free exercise of religion and forbids the establishment of any religious governance. In a 2002 study, 59% of Americans said that religion played a "very important role in their lives," a far higher figure than that of any other wealthy nation. According to a 2007 survey, 78.4% of adults identified themselves as Christian, down from 86.4% in 1990. Protestant denominations accounted for 51.3%, while Roman Catholicism, at 23.9%, was the largest individual denomination. The study categorizes white evangelicals, 26.3% of the population, as the country's largest religious cohort; another study estimates evangelicals of all races at 30–35%.The total reporting non-Christian religions in 2007 was 4.7%, up from 3.3% in 1990. The leading non-Christian faiths were Judaism (1.7%), Buddhism (0.7%), Islam (0.6%), Hinduism (0.4%), and Unitarian Universalism (0.3%). The survey also reported that 16.1% of Americans described themselves as agnostic, atheist, or simply having no religion, up from 8.2% in 1990.