The number of Americans who don’t affiliate with a particular religion has grown to 56 million in recent years, making the faith group researchers call “nones” the second-largest in total numbers behind evangelicals, according to a Pew Research Center study released Tuesday. Christianity is still the dominant faith by far in the U.S.; 7 in 10 Americans identify with the tradition. However, the ranks of Christians have declined as the segment of people with no religion has grown, the survey says.

Between 2007 and 2014, when Pew conducted two major surveys of U.S. religious life, Americans who described themselves as atheist, agnostic or of no particular faith grew from 16 percent to nearly 23 percent. At the same time, Christians dropped from about 78 percent to just under 71 percent of the population. Protestants now comprise 46.5 percent of what was once a predominantly Protestant country. Researchers have long debated whether people with no religion should be defined as secular since the category includes those who believe in God or consider themselves “spiritual.” But the new Pew study found increasing signs of secularism. MORE