The number of Americans who identify as white and Christian now represents less than 50 percent of the United States population. A new study says immigrants have driven the decrease along with a growing number of Americans who reject organized religion. The Public Religion Research Institute, or PRRI, did the study. It questioned more than 100,000 people between January 2016 and January 2017. It found that Christianity overall remains a large majority. Nearly 70 percent of Americans identify themselves as Christian. However, white Christians -- once dominant -- now make up only 43 percent of the national population. Forty years ago, about 80 percent of Americans were white Christians. Today, about 25 percent of Americans do not identify with a single religion.