From Ed Stetzer’s blog:
Around 75 percent of Americans call themselves Christians—they “self identify” as Christians, regardless of how others might define them. I find it helpful to separate those who profess Christianity into three categories: cultural, congregational and convictional.
Now, these are NOT exact numbers, but broad categories. The numbers are different from region to region, but as a whole, the categories might be helpful.
The first category–Cultural Christians–is made up of people who believe themselves to be Christians simply because their culture tells them they are. They are Christian by heritage. They may have religious roots in their family or may come from a people group tied to a certain religion, e.g., Southern Evangelicals or Irish Catholics. Inside the church, we would say they are Christians in name only. They are not practicing a vibrant faith. This group makes up around one-third of the 75 percent who self-identify as Christians—or about a quarter of all Americans.
The second category–Congregational Christians–is similar to the first group, except these individuals at least have some connection to congregational life.They have a “home church” they grew up in and perhaps where they were married. They might even visit occasionally. Here again though, we would say that these people are not practicing any sort of real, vibrant faith. They are attendees. This group makes up another third of the 75 percent—or about a quarter of all Americans.
The final group–Convictional Christians–is made up of people who are actually living according to their faith. These are the people who would say that they have met Jesus, He changed their lives, and since that time their lives have been increasingly oriented around their faith in Him. Convictional Christians make up the final third of the 75 percent—or about a quarter of all Americans….
The “Nones” category is growing quickly, but the change is coming by way of Cultural and Congregational Christians who no longer feel the societal pressure to be “Christian.” They feel comfortable freeing themselves from a label that was not true of them in the first place. Convictional Christians are not leaving the faith; the “squishy middle,” as I like to call it, is simply being flattened.