Agree that you cannot demonstrate a direct correlation between numbers baptised and the final growth rate reported in the YB however it is an indicator of the state of the nation. During the golden age of the WTS in the 50s and 60s assemblies saw large numbers of people baptised. The organisation was growing in good numbers year on year.
If you want to do some back of a fag packet sums....
7000 people is say 7 circuits (or parts of circuits).
We typically see <10 people per approx attendance of 1000 baptised at a CA. So, for the combined assembly/convention for this bunch you have an optimistic forecast of ((10x2)x7)+31= 171 persons baptised over a year. This is 2% growth before accounting for leavers of any type.
If you say only 50% of the district are active publishers doing 10 hours a month (conservative estimate I think) then that's (3500x10)*12 = 420000 hours a year.
That's 2470 hours per baptism. That's over 300 days of 8 hours preaching for one person.
It might be rough figures but it lines up with the sums from the yearly report and is shockingly poor for an organisation supposedly dedicated to preaching the good news and saving lives.
One other point - anecdotal evidence is that the majority of baptisms are of born in children, certainly in the West and other countries where Witnesses are well established.