In a Salon article, Katie McDonough cites a recent survey indicating that 19% of the U.S. adult population is classified as "Religious Progressive."
The rest of the population, per the survey, breaks down as follows:
Religious and conservative: 28%
Religious and moderate: 38%
Not religious: 15%
McDonough's article is linked below.
Katie McDonough at Salon: Religious Progressives Growing in Number
"While politicians like Rick Perry and pundits like Bill O’Reilly may clog up a lot of media airtime, the proportion of religious conservatives in the United States is shrinking with each successive generation, and close to 20 percent of Americans today are religious progressives..."
Katie McDonough, Salon