[Question] If a poverty alleviation intervention has a positive ROI, (why) isn’t anyone lending money for them?

Assuming:

  • There are large funding gaps (ie. not enough philanthropists) for cost-effective interventions

  • Where cost-effective means it does a higher return on investment than the next best alternatives (say the S&P500)

Why don’t egotistically motivated people lend money for all those interventions (to the extent they are not done by philanthropists)?

I understand that it wouldn’t work for public goods, but some interventions aren’t.

For example, why aren’t banks lending money for people to pay to get themselves dewormed?

Possible answers include:

  • Lenders might not be able to enforce reimbursement of the debt

  • Children cannot legally borrow money, or other such legal restrictions

  • Interventions have a lower return on investment

  • There’s too much uncertainty about whether an intervention works, and it would be too expensive to find out in expectation

I feel like I might have asked something similar somewhere at some point, but I’m not sure.