By LIZ A. FOWLERThe American Atheists are celebrating a milestone: a new survey shows that more than half of American adults say they’re atheists.

That’s up from 43% in 2014 and 41% in 2005.

The results of the 2015 American Values Survey (AVS) are available at: www.atheists.org/advocacy/avs-2015-results.

The survey asked Americans whether they are an atheist or agnostic, or if they were unsure.

Those who were not religious in 2015 were asked whether they were atheist or a spiritual or spiritualist.

More than four-in-ten respondents said they were neither.

And almost one-in (79%) of those who said they are not religious said they never have had a spiritual experience, or never felt a spiritual connection to God.

Those who say they are spiritual are more likely to be religiously unaffiliated, with about two-thirds (66%) saying they are neither religious nor spiritual.

The most common religious affiliation among the people surveyed is Protestantism, with 55% of Americans saying they identify with it.

The most common atheist affiliation is agnostic or a little-known non-theistic faith.

The religious unaffiliated make up only 13% of the country’s population, but they account for almost a quarter of atheists and agnostics, according to the Pew Research Center.

The AVS is a nationally representative survey of 2,500 people from January through July of each year.

This year, about 5% of respondents who said there was no religion in their household had no religious affiliation.