Giving multiplier of Giving What We Can

By Vasco Grilo🔸 @ 2025-09-26T16:53 (+15)

Summary

Context about GWWC’s estimates

GWWC estimated their impact in 2023 and 2024 in terms of additional donations to highly effective charities, like GiveWell’s top charities, based on 2 methods.

As in our 2020–2022 impact evaluation, we used two complementary methods to estimate the counterfactual impact GWWC generated through pledges in 2023–2024:

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It is important to note that when measured over a long period of time for a single group of pledgers, these two estimates should theoretically be approximately the same. The choice of how to weight the two methods simply reflects when we attribute GWWC credit for the pledge donations that we cause:

In the Lifetime Giving Method, GWWC calculates the future recorded donations of 10 % pledgers per pledger-year by year of the pledge from the product between:

GWWC also applied adjustments to account for non-recorded donations, and counterfactuals.

My estimates of future recorded donations

I tried to improve on GWWC’s Lifetime Giving Method as follows:

Here are my calculations.

I present below the relative annual variation of the recorded donations per pledger-year for model 1, which I determined from D(s, y + 1)/D(s, y) - 1 = e^b(s) - 1. For the mean slope weighted by the importance of the year the pledge started, I got a relative annual variation of the recorded donations per pledger-year of -3.87 %.

Year the pledge startedRelative annual variation of the recorded donations per pledger-year for model 1
20096.46 %
2010-7.53 %
20113.08 %
201212.7 %
2013-5.61 %
2014-12.8 %
2015-2.87 %
2016-5.02 %
20174.33 %
2018-4.42 %
2019-19.0 %
2020-17.7 %
2021-29.0 %
2022-11.0 %

The table below has the mean regression parameters, and coefficient of determination (R^2) weighted by the product between recorded donations and years of data. I also combine the estimates from models 1 and 2 with a geometric mean weighted by their coefficients of determination (model 3).

Model 1Model 2
abR^2Weight in model 3ABCR^2Weight in model 3
8.78-0.039527.6 %38.5 %8.630.0576-0.0066244.1 %61.5 %

I show below a graph with my and GWWC’s estimates for the future recorded donations per pledger-year.

Cost-effectiveness of GWWC

I made 3 copies of the sheet with the calculations of GWWC’s last impact evaluation, replaced their future non-discounted recorded donations per pledger-year with my estimates for models 1, 2, and 3, and set the weight of the Lifetime Giving Method to 1. I also made a copy of GWWC’s sheet where I simply set the weight of the Lifetime Giving Method to 1.

My models lead to a value of a 10 % Pledge and cost-effectiveness of GWWC in 2023 and 2024 very similar to those from their Lifetime Giving Method. I got:

GWWC estimated 45 % of the pledge donations from 2023 to 2024 went to global health and wellbeing, of which 94 % were high-impact donations. So 42.3 % (= 0.45*0.94) of the pledge donations from 2023 to 2024 went to high-impact global health and wellbeing interventions. I believe these are the overwhelming driver of GWWC's cost-effectiveness accounting for effects on soil animals, which I think is practically proportional to the increase in agricultural-land-years per $. In addition, I guess high-impact global health and wellbeing increase agricultural-land-years as cost-effectively as GiveWell’s top charities. As a result, for my preferred model 3, I estimate GWWC in 2023 and 2024 increased agricultural land 3.56 (= 8.42*0.423) times as cost-effectively as GiveWell's top charities.

I still recommend funding HIPF. I estimate this increases agricultural land 9.42 (= 1.29*10^3/137) times as cost-effectively as GiveWell’s top charities, 2.65 (= 9.42/3.56) times as cost-effectively as GWWC in 2023 and 2024 based on my preferred model 3.

Acknowledgements

Thanks to Aidan Whitfield for feedback on the draft. The views expressed in the post are my own.


Michael St Jules 🔸 @ 2025-09-26T19:22 (+9)

I recommend funding GWWC and the Centre for Exploratory Altruism Research’s (CEARCH’s) High Impact Philanthropy Fund (HIPF) due their effects on soil animals, which I think are practically proportional to the increase in agricultural-land-years per $. I estimate HIPF increases agricultural land 9.42 times as cost-effectively as GiveWell’s top charities, which is similar to my estimates for the giving multiplier of GWWC in 2023 and 2024.

A few quick comments:

  1. GWWC donors don't only give to GiveWell (or other life-saving) charities, so you'd want to discount by the proportion going to them.
  2. There might be other charities that GWWC supporters donate to that will increase soil animal populations in expectation, e.g. some diet change and alternative protein work. You'd probably want to check the net effect combining them.
Vasco Grilo🔸 @ 2025-09-26T20:15 (+4)

Thanks, Michael.

That crossed my mind, but I should have discussed it. I was guessing it would not matter. Based on numbers from GWWC's impact evaluation of 2020 to 2022, the donations to improving human wellbeing were 78.3 % (= 0.65/(0.65 + 0.07 + 0.11)) of those to improving human wellbeing, improving animal wellbeing, and creating a better future (the other category was "Multiple/Unknown"). I had something like that fraction in mind. However, I see now that GWWC estimated that only 45 % of the pledge donations from 2023 to 2024 went to global health and wellbeing, of which 94 % were high-impact donations. So 42.3 % (= 0.45*0.94) of the pledge donations from 2023 to 2024 went to high-impact global health and wellbeing interventions. I believe these are the overwhelming driver of GWWC's benefits, and increase agricultural land roughly as cost-effectively as GiveWell's top charities. So, for my preferred model 2, I estimate GWWC in 2023 and 2024 increased agricultural land 3.53 (= 8.34*0.423) times as cost-effectively as GiveWell's top charities, and 37.5 % (= 3.53/9.42) as cost-effectively as funding HIPF.

I replaced the paragraph before the acknowledgements with the following.

GWWC estimated 45 % of the pledge donations from 2023 to 2024 went to global health and wellbeing, of which 94 % were high-impact donations. So 42.3 % (= 0.45*0.94) of the pledge donations from 2023 to 2024 went to high-impact global health and wellbeing interventions. I believe these are the overwhelming driver of GWWC's cost-effectiveness accounting for effects on soil animals, which I think is practically proportional to the increase in agricultural-land-years per $. In addition, I guess high-impact global health and wellbeing increase agricultural-land-years as cost-effectively as GiveWell’s top charities. As a result, for my preferred model 2, I estimate GWWC in 2023 and 2024 increased agricultural land 3.53 (= 8.34*0.423) times as cost-effectively as GiveWell's top charities.

I still recommend funding HIPF. I estimate this increases agricultural land 9.42 (= 1.29*10^3/137) times as cost-effectively as GiveWell’s top charities, 2.67 (= 9.42/3.53) times as cost-effectively as GWWC in 2023 and 2024.

@Michael St Jules 🔸, I had initially said I removed the last bullet of the summary, but I have now replaced it with the following.