Although this study is interesting in that it compared giving as a percentage of discretionary income rather than AGI, which is a more usual comparison. Therefore the fractions and percentages involved are a lot higher. Interestingly, by this metric, the most generous group is the somewhat above the median in terms of income---call it the top half of the middle middle class.
Also, rich people living outside wealthy enclaves are considerably more generous.
I tend to see things more in terms of AGI honestly, as I view the decision to live in, say, Portland Oregon, as a consumption decision relative to other less pleasant options, but I'm sure lots of folks, especially on the left side of the spectrum, will studiously try to ignore that fact.
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