There's a Wikipedia entry for that: https://en.wikipedia.org/wiki/Windshield_phenomenon
That was a surprise to me! I checked out the Wikipedia article to see if it said "lower numbers are attributed to more aerodynamic windshields," because as a former Scion xB driver for 15+ years I saw the number of splats drop quite a lot. The area I lived in was undergoing a massive shift from farmland to housing developments too though, so I couldn't extrapolate further.