The U.S. Is Retreating from ReligionBy 2030, say projections, a third of Americans will have no religious preference By Allen Downey on October 20, 2017
https://blogs.scientificamerican.com/observations/the-u-s-is-retreating-from-religion/Since 1990, the fraction of Americans with no religious affiliation has nearly tripled, from about 8 percent to 22 percent. Over the next 20 years, this trend will accelerate: by 2020, there will be more of these "Nones" than Catholics, and by 2035, they will outnumber Protestants.
[...]


In fact, there are reasons to think these predictions are conservative:
- Survey results like these are subject to social desirability bias, which is the tendency of respondents to shade their answers in the direction they think is more socially acceptable. To the degree that apostasy is stigmatized, we expect these reports to underestimate the number of Nones. As the visibility of nonreligious people increases, they might be more willing to be counted; in that case, the trends would go faster than predicted.
- The trends for Protestants and Nones have apparent points of inflection near 1990. Predictions that include earlier data are likely to underestimate future trends. If we use only data since 1990 to generate predictions, we expect the fraction of Nones to exceed 40 percent within 20 years.
[...]