"What becomes apparent is a strong negative trend for the Watchtower, as converting Bible Studies into publishers is dropping rapidly. In the early 1970’s, 0.8 Studies and 200 hours resulted in a growth rate around 10%. In the early 1990’s Studies had increased to 1.0 and hours to 220, but the growth rate had fallen to 7%. In the late 2000’s, 1.0 Study and 220 hours only converts to fewer than 3% growth."
Two things make this difficult to analyze: Firstly, that one does not have to be baptised to be a publisher, and therefore many studies start publishing, drop out, may start again, drop out, and so it is extremely difficult to compare baptisms-publishers-growth. One of the biggest branch offices a few years ago stated that 3/4 of the publishers in that country were baptised. Secondly, you would have to find out the age composition of the publishers. In areas with little growth, one would expect an increasing average age and therefore an increasing death rate or increasing rate of publishers ceasing to be publishers because of health/disability reasons. In areas with a bigger growth, average age would decrease and the death rate decrease - but then again drop outs would be not because of age but because of leaving. Continents have huge differences within themselves, too. Africa, as mentioned, with a Moslem North and a Christian centre/South - Europe with a wealthy and predominantly Protestant West/North and a poor and Orthodox East and a in the middle and Catholic South - Asia with Buddhism and Hinduism and Shintoism and China, and therefore with widely different views on life and fate - USA with its different cultures as to Caucasian/Latin/Black cultures etc.
The more one looks at figures like these, the more difficult it is making a meaningfull statement.