Barna leads a church research institute, and is currently the
most-quoted person in the Christian church in the USA because of his
statistical work. To summarize the book's most important conclusions:

* The number of Christians attending local church in the USA is declining
rapidly. Today, 70% of Christians attend traditional churches, but this
will sink to 30-35% in 20 years;
* The number of followers of Jesus who do not attend a local church will
grow from 30% to 70% in the next 20 years;
* Alternative fellowship forms (house church/simple church, post-modern
churches etc.), currently home for 5% of USA Christians, will grow to
make up 30-35%; another 30-35% will live out their faith in the fields
of media, arts and culture; the remaining 5% of Christians attending
non-traditional forms of church will have a family-based spiritual life;
* Conclusion: a minority group presently not even noticed by many will
become the mainstream of North American Christianity in only two
decades.

"This is a revolution, and will change not only the recruiting strategies of
seminaries and Bible schools, but also radically question church building
projects," says Barna. If only half as many people will be visiting traditional
congregational services in 20 years, a smaller building will suffice.
Source: George Barna "Revolution"