Dear Just Asking,
Each person is different of course, however the overall trend as I have seen it is:
Those with the least personal wealth tend to be the most generous.
The nearest I can come for documentation is the life of the Peace Pilgrim (1914-1982). Around the age of forty 1953 she gave away all her belongings except for her toothbrush, comb and tennis shoes, and spent the rest of her life walking across North America, total seven times. She lived her life as a peaceful presence in the McCarthy era, and her food and shelter came from people along the way who would offer.
And for those 28 years of walking, she learned that it was the poor folk who gave the food and shelter, the wealthy much less often.
So I think it is more your second option, those inclined to give do it regardless of their personal wealth.