The motivation behind donating is very different from the motivation behind spending.
No. That would still imply that the motivation of donating would only vary on the bipolar spectrum of having vs not having the money.
I believe that there is another factor when it comes to donating that has a much more prevalant influence - belief, activism, humaneness, politics, call it what you want, but it's not primarily economic in nature.
I see your point, but don't you think the two driving forces are balancing in each act?
Personally, no. But that's of course a subjective opinion. I believe for donations, the economic dimension is mostly irrelevant, so there won't be any correlation between economic growth and the number of donations - volume (as in amounts per donation) possibly more so, but still way less than normal spending.