This year is the 25th anniversary of the 1990 National Survey of Religious Identification. With a sample of over 100,000 interviews, it is the largest study of religious affiliation in the United States. Back then only 8 percent of Americans identified as “nones” or non-religious. Yet, when the successors of the NSRI, especially the 2008 American Religious Identification Survey, found that 1-in-6 Americans (15 percent) were non-religious, the press started noticing.

Today, the Pew Research Center and Public Religion Research Institute find that nearly one-quarter of the population is secular. The infographic below shows how this growth has happened percentage-wise and in terms of real population numbers.