Ever since the great American Prophet Joseph Smith, Jr. found inspiration in the book View of the Hebrews, published by Ethan Smith (no relation) in 1823, and after he claimed to use magical seer-stones in order to translate “Reformed Egyptian” writings found on golden plates that have since gone to heaven, The Church of Jesus Christ of Latter-Day Saints—also known as the Mormons—has been going strong.

Founded in the 1830s, and based on the beliefs that we are all the children of a Heavenly Father and Heavenly Mother, that Native Americans are actually the descendants of Middle-Eastern Jews, and that Joseph Smith, Jr., revealed numerous divinely-inspired teachings and instructions on how to live a spiritually-rich life that can earn you entry into the Celestial Kingdom, the Mormon faith constitutes one of the most successful "new" religions in history. Drawing deeply from the well of Christianity, prioritizing the heterosexual family unit, and maintaining efficacious charitable institutions around the globe, Mormons have gone from a despised and persecuted minority to an accepted member of the family of world religions. And their emphasis on proselytizing and missionizing has netted tremendous success, with more than 16 million members worldwide today.

However, despite their remarkable success over the last century and a half, the Mormons are not immune to secularization. As is the case with most religions here in the United States, Mormon growth is starting to slow. Their strength is starting to fray. The great wave of secularization that has swept this country in recent decades—with more and more people rejecting their religious upbringing and leaving their religious institutions, and many others becoming atheists or agnostics—is also lapping at the knees of the LDS Church.

In her new book The Next Mormons, journalist Jan Riess presents a lot of quantitative and qualitative data attesting to this secularizing trend. Sociologically sound, extremely well-researched and well-written, some highlights from Riess’s analysis include the following:

1. Mormon retention rates are dropping.

In 2007, 70 percent of those raised in the LDS church were still in it as adults, but in 2014, only 64 percent were—and among Millennials, it was down to 62 percent. According to Riess, such apostasy rates are gaining momentum, so that soon, “as many as half of Millennials who were raised Mormon may be leaving the faith.”

2. Mormon faith is weakening.

Eighty-six percent of older Mormons know that “God is real,” but only 68 percent of Millennial Mormons share such a conviction; 83 percent of older Mormons confidently know that Jesus was literally resurrected, but only 57 percent of Millennial Mormons hold this belief; 61 percent of older Mormons firmly believe that God created Adam and Eve sometime in the last 10,000 years, but only 47 percent of Millennial Mormons share this belief.

3. Belief in specific Mormon teachings is in decline.

Sixty-seven percent of older Mormons believe that Joseph Smith was a prophet of God, but only 51 percent of Millennial Mormons believe so; 68 percent of older Mormons believe that God is an “exalted person of bone and flesh,” but only 55 percent of Millennial Mormons hold that belief; 62 percent of older Mormons believe that the Book of Mormon is a literal, historical account, but only 50 percent of Millennial Mormons do.

4. in religion is down.

Whereas 92 percent of older Mormons think religious organizations are a force for good, 62 percent of younger Mormons think so.

5. Key elements of religious participation are down.

While 78 percent of older Mormons watch the General Conference, only 44 percent of younger Mormons now do so.

6. Mormon dominance in Utah is also down.

In 2000, 75 percent of Utah residents were Mormon, but today, only 51 percent are.

7. Mormons are now having fewer kids.

Older Mormons were more likely to have been raised in families with 5 or more siblings, while younger Mormons are more likely to have been raised in families with fewer siblings.

8. Concern over is rising.

While only 24 percent of older Mormons are disturbed by the exclusion of women from the priesthood, 59 percent of younger Mormons are.

9. There is less tolerance for homophobia.

While 58 percent of older Mormons strongly agree that anyone involved in a same- should be considered an apostate and subjected to disciplinary action, only 40 percent of younger Mormons feel this way; while only 20 percent of older Mormons think that gay marriage should be legal in the U.S., 40 percent of younger Mormons do.

In addition to these numbers, ex-Mormons are growing into a critical mass, becoming more outspoken and vocal, and establishing more spaces—both online and in person—for ex-Mormons to vent, find solace, and create community; the best book I’ve read on this rapidly growing community of ex-Mormons is Disenchanted Lives, by E. Marshall Brooks.

Of course, the secularization of Mormonism described above isn’t to be overstated. Most Mormons today continue to find comfort and inspiration in their faith, most people raised in Mormon families tend to stay in Mormon families, and the LDS Church is experiencing significant growth in many poor, under-developed countries around the world.

But the fact that even Mormons—with their extremely tight-knit communities, weekly youth, family, community, and church events, and strong theological convictions—are showing various signs of decreased institutional vigor and rising rates of apostasy illustrates just how powerful the current rise of irreligion is.