The key 73 Congregational Resource Book is unquestionably one of the most helpful manuals for evangelism ever published in America. A study of it can motivate any minister to renew evangelistic efforts in his church, and give him a treasure chest of ideas about how to reach people in his community for Christ.

But the book lacks one ingredient that more and more strategists in evangelism and missions are recognizing as essential to effective evangelism. This missing ingredient is diagnostic research.

Any minister who intends to lead his church out into a year of concentrated evangelistic work needs first of all to determine the health of his church. Once this is done, he needs to write the proper prescriptions and then make appointments farther down the road to see how the patient is doing.

Experience has shown that this is a relatively new concept. I have gone through mountains of Key 73 materials, and have not found anything that suggests it, though some denominational materials that I have not yet seen may include it. The fact is, however, that many are not building this rather essential prerequisite into their Key 73 programs.

Every seminary teaches ministers to consider a church an organism. Professors prove from the New Testament that a church is not basically a human organization but a vital, growing, pulsating body. Christ is the head of this body, and the Holy Spirit is the continuous life force.

But, curiously, few seminaries teach future ministers to evaluate the health of this body. I graduated from a seminary that gave me excellent training in counseling and homiletics but no guidelines for how to tell a sick from a healthy church. No one even encouraged me to think in these terms. When I look back now, I see myself as a civil engineer who has not learned the scales on a slide rule or a physician who cannot interpret an X-ray picture.

Of course, diagnosing church health should not be a one-time event. Like the annual physical check-up, it should be regular—and the older one gets, the more important the annual check-up becomes. Skillful physicians can discover health problems that have not yet shown outward symptoms, and begin treatment before the problem becomes serious. Skillful ministers ought to be able to do the same thing.

Although health is qualitative, the M.D.’s diagnostic research is highly quantitative. He measures temperature, blood pressure, pulse, respiration, hemoglobin, uric acid, sugar content, and so on down a long list. He charts heart activity on an electrocardiogram. The diagnosis of human health becomes very largely a process of comparing quantities.

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Now, of course, diseases can be diagnosed without all that testing, quantifying, and graphing. When the symptoms are pronounced, the patient himself may have a good idea of what is wrong. In countries where medical aid is not readily available, diagnosis is either a do-it-yourself process or is given over to witch doctors who know nothing about stethoscopes. Most human beings, however, prefer modern medicine and trained physicians, when they have the choice.

It is a painful fact that our conclusions on church health have been arrived at more by feelings and guesswork than by modern diagnostic research. In other words, we’re hardly beyond the witch-doctor stage. Some people downgrade church statistics, claiming that they leave the Spirit of God to one side and that, besides, no one was ever saved by statistics. Well, no patient was ever cured by a clinical thermometer either, but patients have been cured by decisions based on the information a thermometer revealed.

Church membership statistics provide the data necessary for diagnosing the health of a church. It is true that membership statistics are not everything. Dedication of the believers to God; the practice of tithing, the family altar, grace before meals; freedom from adultery, drunkenness, envy, backbiting, and other sins of the flesh; love of neighbor, social concern, missionary involvement; Bible memorization, individual prayer, personal devotions; marital harmony—these and scores of other Christian characteristics are related to the quality of church health. But for diagnostic purposes, no facts approach membership statistics in usefulness.

In his remarkable book Why Conservative Churches Are Growing (Harper & Row, 1972), Dean Kelley comes to the same conclusion. He takes pains to answer common objections to membership statistics, such as the charge that they are inflated and unreliable. Then he strongly asserts that membership statistics are the best index we can find of the particular quality he isolates in his book: the social strength of a church.

Membership loss, like human weight loss, may be justifiable and even helpful—but only to a point. If weight loss goes too far, there is no patient left. In any case the physician will want to know exactly why it is being lost. Ministers should be no less informed about their church membership, and this can be done well only through the use of statistics.

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It is necessary to stress church membership statistics to avoid a common error that has produced inaccurate diagnosis. This is the use of Sunday-school attendance as the data base. A huge fleet of buses fanning out in ever widening circles is sure to raise Sunday-school attendance, and that is good. The more children in Sunday school the better. But this figure tells very little about the health of the church, which is essentially composed not of youngsters but of adult men and women who are baptized, who take communion, who support the church financially, who hire and fire pastors, who minister to one another, who decide on church policy, and who win others to Christ.

By themselves, of course, even church membership statistics are not very useful. Skillful handling of them is needed. Here are some guidelines:

1. Plot the statistics on a graph. A simple graph with membership on the vertical scale and time on the horizontal scale is a good tool. The refinements can come later. Carefully study the ups, the downs, and the plateaus over at least the past ten years. The graph will raise important questions about your church’s health.

2. As a basis for comparison, start with the membership point of your church ten years ago and then plot a 25 per cent increase for the ten-year period. This gives a rule of thumb for what is called “biological growth”—it reflects normal additions to the church that should have come from the families who were already members. If your membership growth line is near the biological growth line, or below it, you have found a danger sign that your church may be sick.

3. Calculate yearly growth rates. Compare these on a bar graph. If your rate is holding at 10–20 per cent a year, this is a healthful sign. Keep up the good work. If it is 5 per cent or below, however, and declining, ask yourself and your deacons why.

4. Refine your statistics. Break down annual additions to the church into transfer growth (from other churches), biological growth (children from families already in your church), and conversion growth (people won to Christ from the world and taken into membership of your church). Then break down those leaving your church each year: transfers out, death, and reversions (including excommunication if you practice it). Build these refinements into your graphing, and seek answers to the new questions they raise.

5. Make comparative studies. To a point, health is a relative thing. You will know more about your church’s health if you compare it with the condition of other churches in your area. Be careful to choose only those that are working with the same kind of people as those found in your congregation; churches composed of people from other economic and social or ethnic groupings are irrelevant for this study. Go through steps 1–4 with as many other similar churches as you can, and compare the results. If you find others are growing 100 per cent per decade while your church is growing at only 40 per cent, you have uncovered an important fact. Find out why this has happened. The reasons are there, but they must be dug out.

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Once you have done all this, you will know more about your church than you have ever known before. You should have discovered what you have been doing right and what you have been doing wrong. You have the type of diagnostic research necessary to plan realistically for Key 73 or for any other year of growth for your church.

The next step is to prepare for the annual check-up one year hence. Using today’s membership as a starting point, plot a theoretical line of growth over the next five years. Plot next to it the biological line. This is a test of your faith. Ask yourself, “How many new members can we trust God for over the next five years?” The answer certainly should be more than the biological rate, but how much more depends on dozens of factors concerned with your own local situations.

This is why it is much better if you do not do this alone. Include other leaders of your church so that you will keep one another from unrealistic projections, which can be frustrating. Go through this with other ministers and leaders from your own denomination or others in the community. Build in some procedure that will commit you to accountability to others, just to keep you on your toes.

The more you do this, the better you will be able to do it. At least one theological seminary in America is now teaching courses in this type of church planning. Those of us who did not study it in seminary have to get along the best we can, and allow experience to teach us.

It would be a shame to “spend many long hours in prayer, interaction, study and research in trying to sort out strategy, materials, methods, and suggestions which we feel can be most effectively used in a great evangelistic thrust for our nation,” as the Key 73 Resource Book suggests, and when it is all over, not to be able to look back and accurately report whether the effort was a success or a failure. Many saturation and other evangelistic efforts have ended this way, and it is a pity.

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The health of each one of our churches, and the church in America as a whole, is important enough to receive the best of specialized diagnostic research and prescriptive care. It is important, not because a church is an end in itself, but because our churches are God’s chosen instruments to win those multitudes of pagan Americans to Jesus Christ.

George M. Marsden is associate professor of history at Calvin College, Grand Rapids, Michigan. He has the Ph.D. (Yale University) and has written “The Evangelical Mind and the New School Presbyterian Experience.”

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