The centroids (of hometowns) are moving eastward, but there is little meaningful difference over the years. This could possibly mean that the overall composition of KGP is not random - and is more or less constant across batches - which is incredibly interesting.
JEE ranks of regions and their preference of IITs need to be studied further. Assuming rank to IIT-Department affinity is more or less constant, this could mean that rank to region affinity is also constant, on an aggregate.