“Things could be worse than they let on.”
https://www.jehovahs-witness.com/topic/4801405261447168/comparison-between-jws-lds-sda-mexico
This may help answer that question about the truthfulness of wt reporting methods. Like slim said, it’s when you start comparing other groups, that are similar to Wt, that you realise how well and truthful they are.
Speaking for my own country. Which could be described as a wealthy western country. The census figure has always been, and still is presently, twice that reported by Wt. I’ve heard similar reports anecdotally as well. Interestingly though, I will say, that over the years there has been a slight decrease in the census figure. I explain this in terms of the people leaving the religion, are now not leaving because they can’t be bothered going, but still identify as a jw in the census. But leave because they disagree with the doctrine or the JW culture, hence they don’t identify in the censes. I think the dynamics in people leaving has changed, due to availability of information. However that been said the figure is still roughly twice that of wt.