That's focuses only on the wealthy ($200k income or $1m assets), but within that group, higher incomes consistently donate a greater percentage to charity.
The original research (not NYTimes journalism) is actually from 2001 [1]
1. Of the income groups studied, the highest percentage of income donated was from the <$25k group, with 4.2% ($587/yr), about one percent more than the 3.1% ($1,620/yr) average.
But the study's highest income division was only $100k. Had they included more ranges, they would find that giving goes much higher, e.g. $200k-500k donates 8.3% and $2m+ donates 14.0%. [2]
2. Also in the original study (though absent from the NYTimes article nine years later), is the finding that more people donated at the higher income levels. 77% donated in the lowest income group, but 97% donated in the highest.
And I would give that fact considerable weight for supporting the assertion "if the common folk of Europe were doing economically better, they would have been more generous".
That's focuses only on the wealthy ($200k income or $1m assets), but within that group, higher incomes consistently donate a greater percentage to charity.