This I think is the only award category where there's a clear trend over
time (as of 2020); namely that the range and average number of ratings goes
down. This might be a function of newer books not having had the time to
build up readership to the level of (slightly) older books, or perhaps it
indicates YA is losing popularity, as I've occasionally seen reported.
I don't see a similar trend in the WSFS, Locus or Dragon YA categories, although
of those, only the Locus has been running long enough to be sure about any
trends.
Commentary
It probably won't come as a massive surprise that the winners of these awards are usually one of the top 3 nominees ranked by number of ratings.