During the 20th century up to 1990, the popularity of Christianity had been stable
in the U.S. About 87% of adults identified themselves as Christians.
The country then experienced a major change.
The gradual drift away from religion towards secularism that began after World War II began to have an impact on adult Christian affiliation. Significant numbers of American adults began to leave Christian denominations and from other organized religions. By 2007, the
percentage of Christians had dropped to 78.4%. By 2014, it reached 70.6%. That is a drop of 7.8 percentage points in seven years -- about one percentage point a year. This decline appears to be continuing.