For most of the latter half of the 20th century, religious life in the United States was marked by four consistent trends: oldline Protestant membership was declining; evangelical Protestants were growing; Roman Catholics were hovering just above the replacement level (with new immigrant growth slightly exceeding the amount of erosion in the white ethnic base); and each succeeding generation of adults was participating less in religious institutions.
For the conservative Protestant family, the Yearbook data show a steady slowing of growth that goes back to at least 1955. Growth fell from over 3 percent annually during the 1950s to about 1 percent through the 1980s to less than a half percent through 2005, at which point Southern Baptist declines pushed the entire family into negative growth for the first time.
For oldline Protestants, the Yearbook data confirm a moderating rate of decline during the last 20 years of the 20th century, but show that decline reaccelerated at the turn of the century and that this stream of faith is currently losing members at a greater rate than ever before.