I don't have the exact numbers, but can state anecdotally that the growth in my city is very low considering the amount of time, money, and effort spent recruiting on campus. In fact, the meeting hall has four prominent "No Trespassing" signs that line the entrance. Like most (all?) other localities, there is also no signage to indicate that believers and seekers are welcome to join and worship the Lord.
Maybe someone could argue that this would be a division? Which as Lee puts it, "is on the line of death, originates with Satan, and issues in the great Babylon and, ultimately, the lake of fire."(Genuine Ground of Oneness, CHP 3, Sec 1
http://www.ministrybooks.org/books.cfm?n).
Or maybe they don't need to remove the trespassing signs and instead, as Witness Lee puts it, "God commands us to destroy all other worship centers and to go only to the place chosen by Him." (Genuine Ground of Oneness, CHP 4, Sec 3
http://www.ministrybooks.org/books.cfm?n).