Everyone kept feeling a sense of awe; and many wonders and signs were taking place through the apostles. And all those who had believed were together and had all things in common; and they began selling their property and possessions and were sharing them with all, as anyone might have need. Day by day continuing with one mind in the temple, and breaking bread from house to house, they were taking their meals together with gladness and sincerity of heart, praising God and having favor with all the people. And the Lord was adding to their number day by day those who were being saved. [Acts 2:43-47]
Rather than pure numbers, the healthy church is concerned about character - a character reflected in the embodiment of Jesus in the power of the Holy Spirit. Indeed, it would seem that the concern of the human members of the church described in Acts was to draw closer to Christ in worship and service. This was the work of the Spirit in each member's life. Numbers was the "Lords" concern, not theirs. What 'role' do numbers play then? If Luke mentions numbers, there must be a reason; even if they are not the central concern...
Here is a possible answer: numbers represent the fulfilling of need. The organization that is "increasing" in numbers is fulfilling a need; the organization that is decreasing, is missing the need. This 'need' can be filled in a holy fashion, or in an unholy fashion, resulting in either increase or decrease. In some churches, numbers can increase due to personality-driven leadership, entertainment-oriented ministries and comfort-focused facilities. The focus of this church is not Christ then, but self - yet the numbers increase - because the easiest thing for any organization to do is to appease the self. So numbers can't be the sole indicator of church health. The measure has to be something else.
Rather than numbers, the key to church health would seem to be 'character transformation'. Do the persons who make the church have transformed character? Together, do these people exhibit a community character that could be described as "like Jesus"? The addition of 'numbers' then becomes the responsibility of the Lord (Acts 2:47). The joy of the church then must come from the presence of the Spirit in the transformed character of the people of God. The Western - and particularly the American - church must change its understanding of the function of numbers and the reason the church exists. Indeed, the most satisfied self is ultimately not the comfort-driven self, but the self-in-Jesus.
Small, then, can be beautiful. A church whose members seek self-transformation in Jesus find 'solace' not in creature comfort, but in the cross. Church health then is reflected in a luminous character, imbued by the Spirit in the image of Christ. This luminosity draws hurting people in - some stay and are transformed, and yet some do not stay, finding the cost to self to be too high. Yet growth is present, first in character, then in presence. The healthy church will go through cycles of numerical growth and decline, but will always have a tremendous sense of character in the Spirit due to the abundant presence of love.
In the future, the church will focus on character transformation. The congregations of believers will vary in size, but due to outside pressures, will most likely be small. Rather than focusing on large rolls and big budgets, the church of the future will be smaller, more mobile and will be enclaves of the character of Jesus. Traditional or contemporary, believer or seeker sensitive, emerging or cowboy - those facets will not matter to the church in the future. The question will be - how do you embody Jesus?