From my experience, about half of the contributions in the KH box came from just a handful of families (maybe 3), and they’d usually write a consistent check every month. The people that did this were always well-established families, and they’re getting older and dying off.
About half of the families would give the other half of the contributions, usually in cash. (Since it was cash, it was a little harder to know, but you could tell who walked by the contribution box and slipped something in.) These families were not as stable, as far as I could tell.
My estimate is that about half of the publishers never gave anything. Many of them were along for the social experience, some were mentally ill, in hindsight some were probably awake. This last group will be increasing. Their donators are literally dying off.