Ten social ventures each need a fixed amount of capital and offer two returns: a financial internal rate of return (IRR) and a Social Return on Investment (SROI) โ the dollars of measured social/environmental value created per dollar invested, the "blended value" concept from impact-investing practice. Ventures also carry a 1โ5 risk rating.
Ventures whose risk exceeds the risk tolerance slider are excluded. Among the rest, each gets a blended score:
score(v) = ฮป ยท SROI(v)/SROI_max + (1-ฮป) ยท IRR(v)/IRR_max
Ventures are ranked by score and funded greedily โ highest score first, each taking its full capital ask from the remaining budget โ until the budget runs out; the last venture that only partially fits gets a fractional allocation. This is the classic fractional-knapsack algorithm, provably optimal for maximizing a linear value function under one budget constraint when items can be split.
- ฮป = 0 โ a purely financial investor: capital flows to the highest-IRR ventures regardless of impact.
- ฮป = 1 โ a philanthropic-first allocator: capital flows to the highest-SROI ventures regardless of return.
- Risk tolerance โ mirrors how impact-investing funds screen out ventures above their risk mandate before ranking the rest.
- Re-survey ventures โ redraws each venture's IRR, SROI and risk within a realistic band, as a fresh due-diligence round would.
Top wheel: wedge length is the fraction of each venture's capital ask that got funded โ drag left/right to rotate the wheel. Bottom chart: each venture plotted by IRR (x) vs SROI (y); a filled dot is funded, a hollow ring is screened out or unfunded; dot size tracks risk.