Part of the problem is that for every new convert they might get from the door to door work or from family preaching, they lose one to the DA or DF policies.
It has been true that at least 75% of new JWs are JW children being baptized. Some Kingdom Halls have over 25% of their membership consisting of teenagers between 12 and 19. The problem for the WT is that those are the very ones who will drift away or be DF'd as soon as they leave home. The good news is that they are typically replaced by more kids attaining the age of 12 or more. You still see a lot of 7, 8, and 9 year olds being baptized and they go on the publisher roles as soon as they do.
An adult convert, other than a non-JW spouse who finally converts or a close relative like siblings who move in with JWs due to financial or family issues, is still quite rare. I asked a DFd fellow who had been a CBE until his leaving how many converts he had actually met. He served in two KHs and he told me that both had no adult converts in recent memory and definitely none while he was serving there. He mentioned that the last major conversion he heard about was when the male member of a family raised as Mennonites and then shunned by their community converted to JW (cult ----> cult) and brought his whole family of eight into the the KH. They all got baptized within a year, so the congregation showed a +10 growth one year when they were combined with the +12 year olds who were already attending.
Think about it. An annual growth of 1 or 2% should be expected just from children and close relative conversions. Conversions due to Memorial invitations or local convention walk-ins are now miniscule compared to the 1950s and 60s when these were relatively common. I remember that quite a few, escpecially in the New York, San Francisco, and St. Louis areas became converts because of the temporary housing work (asking the public to allow the brothers to rent spare rooms during a convention). They would see the JWs come visit for 5 to 8 days and notice that they were well-behaved and otherwise good citizens - and would become interested from that experience. I don't know if that work is still a part of convention prep - or if that has been replaced by using current JWs and hotel discount programs. Some one will have to up date me on that. But if you fit 50,000 families and individuals into a large city renting rooms from the public, there has to be some conversions related to that.
What I find amazing is that more DFing seems to happen in smaller congregations ( < 100 baptized members) than larger ones (> 125). A nearby congregation DF'd a MS a couple years back and his whole family (wife, sister-in-law, and 5 minor children) were all out within months. Eight people in a small congregation suddenly disappear forever and the KH looks pretty empty on a Thursday night.
JV