A sliding scale for donation percentage

I absolutely love this @Thomas Kwa. Something along these lines of thinking has been a deep part of my Christian tradition, from the parable of the widow's mite

"Just then he looked up and saw the rich people dropping offerings in the collection plate. Then he saw a poor widow put in two pennies. He said, “The plain truth is that this widow has given by far the largest offering today. All these others made offerings that they’ll never miss; she gave extravagantly what she couldn’t afford—she gave her all!”

Obviously this is a bit more "deontological" and "heart focused" reasoning but agrees in practise with your comment "one should obviously give up more utility if beneficiaries gain more per unit you sacrifice"

I used to argue that someone who earns 100k and gives 10% has in a non-utilitarian sense might have  given "more" than someone who earns $200,000 and gives half away. But I think I almost like your "sliding scale" more as there's some nuance there.

Your table is very similar to the one Peter Singer presents close to the end of The Life You Can Save. I do like the mathematically clarity of your approach, and we now have an intuitive explanation for where the numbers come from - very nice!

Honestly, now that I write this it seems strange that there is no Pledge that matches this way of thinking? Your suggestion could be a nice complement to the existing 10% and Further Pledge and it now seems a little strange that I have not heard about people actively donating according to Singer's table. Maybe it is just a lot harder to explain than the other pledges, and this kind of defeats the point of a public pledge?

In case someone else wonders what the donation rate would look like for other choices of $\gamma$:

I think a pledge which puts the bar for zero donations at the US-median income  [edit: oops, I got that wrong and it is not the median income value. I still think that my point is directionally right] is a little strange – even in the US, many pledgers would never reach non-zero pledged donations and this seems off for a pledge that has income-sensitivity as a central property. Intuitively, a softer rule like "in any case, aim for 1% donations unless you really need all income" or a different reference for the zero-donations bar would be more wholesome.

Thanks Thomas. I largely agree with your suggestion. I wrote a paper on the topic, with a few additional ideas that might interest you and others here. https://www.tandfonline.com/doi/full/10.1080/16544951.2023.2246257 Besides income, I think it's worth considering a few other relevant factors, including net wealth. 

This was pretty much the first thing I thought of when I heard about the 10% pledge, and I was actually surprised to see so little of this reasoning here. It’s fairly obvious that for someone on a low income, 10% is still a huge sacrifice, whereas for the wealthy, giving away 10% doesn't change much. Even though they give much more in absolute terms, they’re still left with far more money than they actually need.

This is especially important from the perspective of the rich: with 'only' a 10% commitment, a lot of potential generosity goes to waste - money that could make a massive difference. But it would also help those on lower incomes, allowing them to join the pledge without it being financially draining. That said, I think the percentage should never drop to zero; psychologically, it would imply that low earners can't or shouldn't contribute. Not only is that untrue, but it would also feel very 'exclusionary' for many.

Finally, I’d say the calculation should be adjusted for the cost of living and local salaries. For instance, $39k might not be much in the US, but in many other countries - and not necessarily poor ones, like where I live - it’s actually a good salary.

Mostly like the post, but;

I mostly view the 10% pledge as a social commitment device rather than a sensible rule for how much to donate.

strikes me as missing the fact that small donors can spend much more cognition evaluating per unit dollar and are less heavily optimized against, so there are many high EV opportunities which can ~only be picked up by small-scale donors. Especially within-network donations to support projects that are too early stage or speculative to pass grantmaker bars.

Really enjoyed this post thanks. I agree that "the 10% pledge as a social commitment device rather than a sensible rule for how much to donate". It's memorable and simple which is part of its effectiveness, but I like the analysis into the logic and maths of giving which will appeal to whose brain operates that way.