[Rapscallion St Croix]

I have no empirical data on this issue and can only speak for myself.

I shall assume that waving includes all forms of social initiation such as winking, nodding, smiling, grinning, or the utterance of many words or word-like words, including all variations on hello. Waving is a binary behavior. One is either a waver or is not. I grew up in a culture where friendly greetings are the norm, but I realize that, being a small town Southerner, I am in a small minority here in The Villages. In fact, when I hear a Southern accent, I stop that person and demand that they speak to me in my native tongue. Realizing that I now live in a less culturally homogeneous slice of society, I have morphed towards the following behavior:

I wave at those who have shown me a traffic courtesy
I wave at all those I know and whom I think know me
I wave at first responders and military
I wave at those who have Saints, Most SEC teams, USAF, or Grateful Dead decals on their carts
I return all waves regardless of number of fingers used
If my wave is unreturned, my reaction varies from none at all to sub-vocalizing the easiest to lip read two word phrase in the English language