Mormons are by far the most religious of any group in this analysis, based on self-reported importance of religion and religious service attendance, followed by Protestants/other non-Catholic Christians and Muslims. Catholics are slightly less likely than these groups to say religion is important in their daily life and that they attend religious services frequently. Those who identify with a non-Christian religion other than Judaism or Islam are less religious still. And Jews are the least religious group measured.
Survey: 53% of Americans identify as Protestant, 24% as Catholic, 18% as unaffiliated