Less insecticide is probably the key thing.

Driving in the eighties with windscreens full of insects, and now hardly anything, and a lot less of the things that lived on them.

Sometimes I wonder about that. The measure is number of insect impacts on windshields but is the car the same?

If we use a more modern care would the increased aerodynamics prevent impacts as instead of punching through the air you are cutting through it?

Have never read the full experimental setup and assumptions... I do know that I have less dead bug then when I was a kid...