To be clear, I don’t mean ‘graph of how the expected multiplier on a dollar changes over time’, I mean ‘graph of how the expected donations generated by a dollar given are distributed over time’ (before any discounting).
This is something Sjir’s team and myself have discussed at length—we’re definitely more pessimistic than GWWC on this point.
CEARCH’s view is that the raw numbers look good, but if you regress dollar donated against year since pledging, while controlling for pledge batch (and hence the risk that earlier pledgers are systematically different/more altruistic), there is a positive but statistically insignificant relationship between average annual donations and years since pledging (n.b. increase in 35 dollars per annum at p=0.8). The experts we spoke to were split, with a weak lean towards it increasing over time—some were convinced by the income effects, while others were sceptical that you can beat attrition.
Ultimately, we chose to model a very marginal increase (<0.01% per annum); we’re really not confident that you can reasonably expect an increase in giving over time for the 2025 and future pledge batches.
For how expected donations generated by a dollar evolves over time (ignoring discounts), available evidence suggests that it’s flat (and so the graph is just a horizontal line terminating around 30 years later). There’s a lot of uncertainty, not least on how long the giving lasts, given that we can only observe a little more than a decade of giving at this point.
To be clear, I don’t mean ‘graph of how the expected multiplier on a dollar changes over time’, I mean ‘graph of how the expected donations generated by a dollar given are distributed over time’ (before any discounting).
You may be interested in this chart from the What trends do we see in GWWC Pledgers’ giving? subsection of GWWC’s 2020-22 cost-eff self-evaluation, as well as their discussion:
This is something Sjir’s team and myself have discussed at length—we’re definitely more pessimistic than GWWC on this point.
CEARCH’s view is that the raw numbers look good, but if you regress dollar donated against year since pledging, while controlling for pledge batch (and hence the risk that earlier pledgers are systematically different/more altruistic), there is a positive but statistically insignificant relationship between average annual donations and years since pledging (n.b. increase in 35 dollars per annum at p=0.8). The experts we spoke to were split, with a weak lean towards it increasing over time—some were convinced by the income effects, while others were sceptical that you can beat attrition.
Ultimately, we chose to model a very marginal increase (<0.01% per annum); we’re really not confident that you can reasonably expect an increase in giving over time for the 2025 and future pledge batches.
For how expected donations generated by a dollar evolves over time (ignoring discounts), available evidence suggests that it’s flat (and so the graph is just a horizontal line terminating around 30 years later). There’s a lot of uncertainty, not least on how long the giving lasts, given that we can only observe a little more than a decade of giving at this point.