I should like to correct an impression you seem to have that is incorrect:
Since the WT Society only reports those that are actively preaching, they are in effect, under reporting the actual figures when compared to how other religious groups count their members.
Perhaps you got your impression from the WTS who are often seeking to paint churches in the worst possinble light but the facts are these:
1. Churches I know have a Service Register in which is entered the particulars of the services, including attendancew of adults and children.
2. When the Diocese is reviewing the size of the church, it is the figures in the Service Register that are used.
In other words, only active churchgoers are included in the numbers for a church.
Of course, in a government census many people who are non-churchgoers may register themselves as belonging to a particular church butr this doesn't mean that the church itself is including them.
I trust that this clarifies things for you.