I thought Jiles Grey response to this question was interesting:
"I think that it demonstrates just how ineffective the Jehovah’s Witnesses’ door to door evangelising is.
In 2019 there were 303,866 people baptised. This was during a year when the preaching work was in full swing.
In 2020 there were 241,994 people baptised. This was during a year when Covid halted much of the preaching work.
The fact that there was only a difference of -61,872 new converts indicates just how many of the newly dedicated people are in-house, many of them being children of JWs who have been brought up in the religion. It would be very interesting to see the data on the average age of the baptismal candidates.
Considering that the numbers of those who were baptised last year are considerably less than the 297,872 people who were baptised in a single year in the mid 70s (when the number of publishers was only around 1.5 million, compared to over 8 million in 2019/20), last year’s numbers, and even those of 2019, are not at all encouraging.
The two decades from the year 2000 has shown that the growth of the Jehovah’s Witnesses has reduced dramatically, from 11.92% during the years 1996 to 2000, down to a mere 3.59% during the years of 2016 to 2020.
Like most religions, the growth of the Jehovah’s Witnesses has been stagnating in recent years and last year showed the first reduction in membership since 1978."