A new Gallup poll has found that Americans are far less religious than they used to be.

Although the United States is considered one of the more religious Western nations, a new Gallup poll has found that Americans are far less religious than they used to be.

According to the poll, the percentage of U.S. adults who belong to a church or other religious institution has plummeted 20 percentage points over the past two decades, hitting a startling low of 50% last year.

Previously, church membership held steady at 70% or higher for most of the 20th century. That figure has fallen steadily since 1999, however, with the percentage of U.S. adults with no religious affiliation jumping from 8% to 19%.

Nancy Ammerman, a professor of the sociology of religion at Boston University, told the Associated Press that the overall decline in church membership is driven by a combination of cultural and generational factors.

"Culturally, we are seeing significant erosion in the trust people have for institutions in general and churches in particular," she explained. "We are also seeing a generational shift as the ‘joiner' older generation dies off and a generation of non-joiners comes on the scene."

The numbers support Ammerman's generational theory. Between 2016 and 2018, church membership among Americans 65 and older averaged 64% percent, compared to 41% among those aged 18-29.

"The challenge is clear for churches, which depend on loyal and active members to keep them open and thriving," Gallup poll analyst Jeffrey Jones noted. "How do they find ways to convince some of the unaffiliated religious adults in society to make a commitment to a particular house of worship of their chosen faith?"

"These trends are not just numbers but play out in the reality that thousands of U.S. churches are closing each year," Jones added. "Religious Americans in the future will likely be faced with fewer options for places of worship, and likely less convenient ones, which could accelerate the decline in membership even more."