I'd say most of my road rides are solo (especially in current state). My sanctuary. But, that said, I do make a point to take off my left hand and drop a low wave to everyone passing on the other side, when safe.

I'm ballparking this.

Age <60 I would say 75-80% wave back, many initiate
Age >60 I would say 30-40%

Women any age 75-80%

Is this just my town? What gives?