Excellent question. My thoughts: the Society is "winning" but the margin is shrinking. Developed countries have zero or negative growth; according to WT spokesman JR Brown's May 10 WNYC interview, they are growing at 1.7%, which I believe (just a guess, tell me if I'm wrong) is less than the growth of the world's population.
On that same interview, then projected a doubling of members by 2020, but at 1.7% I would estimate a doubling would take 42 years, i.e. doubling by 2040. But I don't expect they can continue even the tiny 1.7% growth for very long, the more time that passes, the less credibility their end-of-days preidictions are.
Also, with the Internet and its most popular tool, the World Wide Web, and the free-exchange of information that goes along with it, I *hope* that the truth about "The Truth (TM)" will be exposed like never before.
Remember, information is powerful!
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