Managing Diversity (Not)

I am known for promoting a diverse Church: age, race, status, and so on. This means truly diverse -- not a token diversity. It is for me a sign of spiritual health. But say a Church lacks diversity and drifts towards diversity? Say an 80% White Church becomes 50% White. Or an 80% elderly Church becomes 50% elderly. The congregation may now be fearful. How do we know that we won't be 20% White or 20% elderly tomorrow? What guarantees that this is not an unbalanced shift, or a shift out of control? I think now of a Church which went from 50% White to 90% Black in a short time, while the surrounding area was mostly White. OBSERVATION: I think a balanced diversity is guaranteed through a true "ministry by members" (the priesthood of believers). My best guess as to what went wrong in the 90% Black Church is that they did not actively (above all spiritually) promote people in the Church, without respect of persons. Through such promotion, one creates a culture which truly embraces all. Of course, an alternative is to appoint a Church leadership which engineers things as desired, but in that case it is likely at the expense of ministry by members, and in my own tradition would not be Congregational.