I don’t know of any so can only speculate.
There may be a bandwagon effect in that JWs see the number rising each year since 2007 and this emboldens yet more to partake.
Removing “faithful and discreet slave” status (in 2012?) may have been in part an attempt to discourage others from partaking. However it may have backfired and encouraged a few more to partake if they figured that the new teaching meant that claiming to be anointed was no longer as a big a deal, or egotistical as it used to be.
There were rumours that Paul Gillies began partaking a few years ago, perhaps in an attempt to get appointed to the GB. But presumably ambition to join the GB is only a factor for a minority of new partakers, since not many are realistically in a position to view it as a likely prospect. But who knows? The GB are much more prominent in the last ten years, so ambition to join the GB may also have increased over that period and been perceived as being within easier reach because of their ubiquitous visual presence.
It is also surprising that the reported number has increased so much because it is presumably a number that Watchtower could easily falsify if they wished. Numbers are not reported for individual countries, so who would know if Watchtower underreported the figure, as it would be near impossible to independently verify. So the large increase seems to indicate either 1) Watchtower are being honest about the increase even though it is apparently against their interest and tends to undermine their teaching/authority or 2) the increase has been even larger and they are in fact underreporting the true figure to the extent they deem feasible. Either seems possible.
It has sometimes been mooted that “confusion” among converts in countries in places such as Africa may account for the recent increase. It sounds like clutching at straws but who knows there may be something to it. Independent Watchtower movements have been common in Southern Africa, and it would only take the aberration of a small region with a different perception of the propriety of partaking and claiming to be anointed to boost the worldwide numbers by thousands. The number of partakers for individual countries used to be reported in the Kingdom Ministry, but not for many years. Unless they ever publish these numbers again we won’t know which countries tend to account for the increase.
Above all of this, I think there is a general loss of authority and credibility of the Watchtower leadership in the past couple of decades, and the rising anointed figure may in various ways be a manifestation of that breakdown in authority. “These guys clearly don’t know what they’re doing—see overlapping generation craziness—so who are they to tell me not to partake?”