Stats can be so deceiving. First of all, the JW's 4.4% growth is only 50,000. The Pentecostals had over a 150,000 growth per year! It's a higher percentage of a small number versus smaller percentage of a big number. Do JW's care about saving PEOPLE, or just increasing the percentage of the people they are saving?
Also we know the JW's are quite liberal to count their numbers. If I recall it was active publishers that are only counted. We know many people are hanging by a thread and doing minimal actual service, or in many cases lying or exaggerating their hours.
It's all about quality vs quantity.
On another note, I'd be curious on the number growth of those who are not religious at all. I bet that's growing even faster.