I spent five minutes with Google:
Dataset of the Day: Who is more Generous? Republicans or Democrats?
"So are liberals stingier than conservatives?. The data has suggested that they are. One thing that I am unhappy with is that this data is somewhat dated with the most recent year being in 2004 for philanthropy stats from the Catalogue of Philanthropy. I am anxious to see if the trend has continued into the present and am eager to compare 2008 charity figures with red and blue states from the 2008 Presidential Election.
Overall, I like how Kristof does not see the data as a negative, but a way to encourage more of his fellow liberals to contribute more. He states in his article, 'Come on liberals, redeem yourselves, and put your wallets where your hearts are.'”
There were lots more. Perhaps if we read them all we could draw better conclusions. This is a start.