Sociologists from the University of California, Berkeley, and Duke University analyzed results from the General Social Survey and found that the number of people who do not consider themselves part of an organized religion has jumped dramatically in recent years.
Back in the 1930s and 1940s, the number of "nones" -- those who said they were religiously unaffiliated -- hovered around 5 percent, Claude Fischer, one of the researchers with UC Berkeley, told The Huffington Post. That number had risen to only 8 percent by 1990.
But since then, the number of people who don't consider themselves part of a religion has increased to 20 percent.
"This was not happening really for decades, until around 1990 when it started to take off," Fischer told HuffPost. "One thing striking is the trend in terms of renouncing religious affiliation you might say continues to move up at a regular pace, while there is hardly any perceptible trend in the percentage of people who express atheist or agnostic beliefs."
However, it should be noted that the research looks at whether or not a person associates himself with a particular faith; it does not measure how spiritual a person considers himself to be.