PRINCETON, NJ --According to a recent Gallup Poll, one in six adult Americans living today -- or 35 million people -- recall having heard Graham in person at some point in their lives. In addition, more than half of Americans, 52%, say they have heard Graham on the radio, while 85% have seen him on television." 

A media guide for journalists covering Islam.

The North American Mission Board estimates that 70 percent of the United States population, almost 200 million people, are lost; yet the Barna Research Group indicates that 85 percent of the population self-identify themselves as Christian—what gives? The truth of the matter is that there are a number of different measures of the religious composition of the United States, and it becomes necessary to understand the definitions and sources of the statistics being used.

• The 85 percent mentioned above is an example of religious preference data. This figure was derived by asking a large sample of adults “What is your religious preference?”
• The Gallup Organization collects similar statistics and estimates somewhere around 80 percent of adults consider themselves Christians.
• In a similar vein, Gallup reports that 95 percent of the population believe in God or a universal spirit, 92 percent state a specific religious preference, and 86 percent say religion is at least fairly important in their lives. So, it seems that most people are, to some extent, religious.

Assessing the Nation’s Religious Composition, full report