My view (for what it is worth) is that the foreign language field is masking a continued small but noticable downward trend in the number of publishers. Like other posters , I have noticed very few "new ones" other than children of JWs being baptised. The number of deaths and faders / DFd never to returns must exceed this.
Roughly , the increase since 2001 marked the beginning of the surge in immigration and foreign language groups. I don't have any accurate figures , but assuming 11 COs on the "foreign circuit" , there must be upwards of 6 - 7 ,000 in these congregations & groups , including over 1,000 Chinese. Although the majority are existing JWs who are learning a foreign language , that still leaves a couple of thousand new foreign ones.
The "Polish" effect is not to be discounted , as well. I've heard that over 2,000 JW Poles have moved in to the UK over the last couple of years , swamping the locals in areas like East Anglia & London. (There are congs with 80 Poles sitting in the back , who weren't there last year). The figure seems accurate , as it would roughly tie in applying a 1 in 300 ratio to the 600,000+ Polish immigrants since 2005. Add the Russians , Lithuanians etc etc and this would explain the increase.
Just a couple of further observations. August always used to be the "peak" month , but I don't think that is the case nowadays. The cong effort used to be to get the figures up for the end of the service year , but I haven't seen any WTS sponsored effort in recent times.My own feeling is that the peak is usually in May , but I don't have any figures to back this up.
Also , if a publisher doesn't book hours in one month , but puts two reports next month , then they aren't counted as two publishers. Personally , I have always regarded the WTS as quite meticulous , even picky , in trying to be as accurate as possible with figures.