A survey conducted by Ryan Burge, an instructor at Eastern Illinois University, found that the largest single number of respondents claimed "no religion" as their preference (23.1%), exceeding Roman Catholics (23%) and evangelicals (22.5%). According to the CNN article,
"'Religious nones,' as they are called by researchers, are a diverse group made up of atheists, agnostics, the spiritual, and those who are no specific organized religion in particular. A rejection of organized religion is the common thread they share.
'It is the first time we have seen this. The same questions have been asked for 44 years,' Burge told CNN.
The meteoric rise of religious nones began in the early 1990s and has grown 266% since 1991, he said.
Burge estimates that 'No Religion' will be the largest group outright in four to six years." (our emphasis)There's speculation about the cause for the rapid rise in "religious nones," including social media facilitating connection among non-religious people and younger Americans rejecting religious doctrine in favor of questioning ancient beliefs and superstitions. For Catholics, it may also reflect disgust with the Church's handling of sexual abuse cases, and its cases of financial corruption. For millennial evangelicals, the evangelical movement's continued hypocrisy concerning sexual assaulter and sociopath Donald Trump and support for reactionary social policies seems to be a major driver.