Talking to a PIMO cousin about this subject ( a sister in his congregation has recently started partaking ) he is of the view that with the ditching of the 1935 teaching and the appointment of younger GB members , there simply isn't the stigma that there used to be when people suddenly announce they are "anointed". This is despite the Society trying to discourage new partakers by suggesting they are mentally unstable etc.
In percentage terms as well , there only needs to be a tiny number of new partakers in percentage terms to shift the numbers. The increase of 12,000 or so in the last few years only equates to one in every 700 JWs becoming "anointed" - that is basically 1 JW in 10 congregations in a 12 year period.
In addition , most of the new partakers are relatively young so the residual number is hardly decreasing as people die off. The sister in my cousins congregation is in her 40's , so she ( presumably ) will potentially stay on the anointed list for 40 years or more. There also definitely is a copycat effect as well- my cousin is convinced that the sister was influenced by another JW in a neighbouring congregation doing the same.
In terms of demographic etc - purely anecdotally and on only a small sample - generally middle aged 2nd generation lifetime indoctrinated female JWs.