I suggest you check out ideas42's research on this topic. It's funded by the Gates Foundation and there is more work underway now that I assume will be written up at some point.

By the way, one interesting 'data anecdote'; in our recent donations post for the EA Survey we compare

• the distribution of planned and actual donations for a particular year
• the difference in these for the (minority subset) of individuals who reported in subsequent years
• current vs future donation plans.

Depending on your reading of the data, it possibly suggests that people tend to 'plan to donate' more than they 'actually donate'. But that might not be an effectiveness-specific observation.

Some of my research (past and ongoing) aims to address this.

See innovationsinfundraising.org for a broad overview (not just effective, but aiming in that direction).

Our project "Increasing effective charitable giving: The puzzle, what we know, what we need to know next" is not only about small behavioral nudges, but it certainly gets at this.

My own recent impressions (and perhaps a growing consensus) is that nudges may have been a bit oversold in some domains. But I still see potential.