The downtick in the percentage of the U.S. population identifying as Christian over the past eight years is a continuation of a trend that has been evident for decades. In Gallup surveys in the 1950s, over 90% of the adult population identified as Christian, with only a small percentage claiming no religious identification at all or identifying with a non-Christian religion.

Despite these changes, America remains a predominantly Christian nation, and with 94% of those who identify with a religion saying they are Christian.

The broad Christian category includes Catholics, Protestants, Mormons and non-denominational Christians. In 2015, 24% of Americans identify as Catholic, 50% as Protestant or as members of another non-Catholic Christian religion, and 2% as Mormon.