Valient wrote:... anyone know the ground truth on this one?
It is dependent on the area of the church. In the United States and Canada there are numbers used for organization membership and attendance over a period of time, worthy Melchizedek priesthood holders necessary to fill leadership callings, and other statistical determinants. There is no requirement for the number of youth and children. There is also leeway for the Area Authority to receive inspiration to make adjustments for local conditions and circumstances. If you are looking for exact criteria, no one here can give that. After a branch becomes a ward there can be a downturn in membership, attendance, and available worthy Melchizedek priesthood holders to fill leadership callings. The stake president, area coordinating council, and area authority watch these things and will discuss necessary unit boundary realignments when appropriate.
The organization of the Church is set out in scripture. Derived from that we have a living document in the General Handbook that provides further guidance for our current day and circumstances. General Handbook, sections 5-15, describes the organization of the Church. After describing the General and Area Leadership in section 5 the Stake Leadership is described and outlined in section 6. One sentence in section 6.1, Purposes of a Stake, states: "Today the Church is organized into stakes."
The organizational goal is to build stakes. Within section 6 is the organization of a stake. Notably there is section 6.3 which outlines the differences between the authority of district presidents and that of stake presidents. In reading that section we can get an understanding as to the differences in organization of a stake and a district. We get an understanding that a district is performing some of the functions of a stake under the leadership of a mission president.
As mentioned earlier in this thread, stake child unit organizations are wards and branches while child unit organizations of districts are branches. For a branch to become a ward it must reside within a stake. I have gone through the processes of making a branch a ward, splitting wards, and reorganizing ward boundaries to combine three wards into two, splitting stakes, and so on while serving in several stake callings and listening to general authorities and area authorities speak on the topic in meetings devoted to those organization changes. While numbers were discussed, they also were focusing on the stability of the unit in the future and meeting the needs of the membership.