A new study shows a significant increase in the number of Americans who say they are not affiliated with a particular religion.
The findings of the Pew Research Center indicate nearly 20 percent of all Americans now consider themselves agnostics, atheists or "nothing in particular" when it comes to religious affiliation, a rise from 15 percent five years ago.
Researchers say the number of religiously unaffiliated Americans is even higher among younger adults, accounting for 32 percent of those under the age of 30.
The study, released Tuesday, could have implications for the presidential race between U.S. President Barack Obama and Republican challenger Mitt Romney, as their campaigns seek to strengthen their appeal to voters ahead of the November election.
The study found almost a quarter of registered voters who identify themselves either as Democrats or Democratic "leaning" say they are religiously unaffiliated, a rise from 17 percent five years ago.
Among Republican and Republican "leaning" voters, the percentage of those describing themselves as religiously unaffiliated grew from 9 to 11 percent over the past five years.
Researchers say the factors behind the increased number of religiously unaffiliated people in America, historically a deeply religious nation, include "generational replacement" — the gradual replacement of older generations by newer ones — and a rise in the number of Americans raised without a religious affiliation.
In spite of the increase, researchers say not all of the religiously unaffiliated are strictly secular, with many saying they do believe in God, pray daily or consider themselves "spiritual but not religious."
The findings are based on several broad surveys conducted by Pew and the PBS television series "Religion and Ethics Newsweekly."