Long ago I learnt that you can study the church/churches as a social phenomenon like a scientist studies a bacteria under a microscope.
You can put the churches in a fish tank and watch them from the outside, study them from purely humanistic eyes, looking at them as social movement. In other words from a purely human behaviour standpoint.
For example you can look at it like an organization providing some service to the public - the service might be care giving in exchange of some donation. So you can get into service delivery and how to improve such service.
My reading of the Bible seems to the suggest that there is some social reality to the church, but overall it is much more than that. In fact I see it as unique grouping of people, something that is so different from the others in the world.
It stands in a category by itself.
For this reason, you can really screw your mind up if you rely on George Barna to tell you what works in church and what does not work.