Understanding How to measure professing and affiliated believers brings in other issues of measurement. If you have an estimate of the total number of “Christians” in a country (in the widest sense), then you can say the following:

Total Christians - Total Professing = Total Secret

and

Total Christians - Total Affiliated = Total Unaffiliated

On a few isolated and rare occasions, I’ve heard it said those who will not profess Christ publicly are not Christians–that a faith that does not brave persecution is not true faith at all. I generally think this view is held by people who don’t have to endure persecution.

Secret believers are “known” because they are estimated as affiliated members of a church, but they don’t show up on government censuses or public opinion polls. Generally this is because these believers decline to state their religion in public areas, or, in some cases, lie about their religion, in order to avoid persecution. Censuses have been used in some countries to identify Christians in order to target them.

In most cases the total number of these believers must be estimated, and the estimates should be treated with care since they can contain significant levels of imprecision. Researchers try to get them into the right “order of magnitude,” but sometimes fail.

Estimates are gathered from a variety of in-country sources. No single source should be relied upon, generally speaking. And, when you read an estimate, remember it is subject to change.

For example, in the first edition of the World Christian Encyclopedia, very little information about the church in China was available. The WCE estimated the total number of crypto-Christians (secret believers) at 2 million in 1970, declining by net 20,000 yearly. By 2000, the WCE projected, total secret believers would number just 1.5 million.

How a few years changed the estimates! In the second edition of the WCE, the number of believers in 1970 was lowered to 1.5 million, but the number in 1990 had swelled to 64 million, and by 2000 the WCE estimated there were some 89 million believers. There are many other estimates besides those in the Encyclopedia, some much more conservative and some much less.

Estimates of secret believers, then, should always be treated as just that–estimates. View them with a grain of salt. Don’t discount them immediately, but don’t take them exclusively at face value either.