As I originally presented in the Finance Perspective for the Institute for the Future's Ten Year Forecast, there are two ways to talk about the value of intangible assets, which is the fundamental issue of Impact Investment:
(1) Return on Investment. In order to do this properly, it's crucial to link to all possible outcomes of an investment to gauge the impact the investor cares about, and hopefully to understand the context well enough to parse out any environmental influences. For financial investments, we note financial return. For community investments or development-oriented investments, there are specific outcomes to note... and it gets complicated quickly.
Take a simple business situation where the question is what is more important: immediate cash flow or trusting interpersonal relationships? Assuming we identify that we need both, how much cash do you put into social capital building and how do you measure its financial value? This is "difficult" because it's impossible, without knowing a lot of related data.
(2) Risk Management. I suggest you examine using risk management as the primary way to value intangible assets. It may not be obvious what strong social relationships bring in financially, but it's certainly obvious what risks need to be mitigated. (And in thinking this through, a heuristic emerges that facilitates decisionmaking that is actually in alignment with value creation... but that's another post.)
Risk Management can be well understood by traditional investors and financially conservative people: you figure out the amount of financial risk, and then the probability -- often scenario based -- of that risk occuring. So if a risk is a $10 billion threat, and it has 0.001% chance of happening, mitigating that risk has a value of up to $100,000.
What's the risk of not having customers in the future? Of your marketing program not working? What's the financial risk of a severe flu season vs a minimized one?
The more complex questions, but the one that can be used to build alliances: what's the risk of an uneducated group of parents to the local hospital, and the risk of a population that doesn't manage their own health well for the schools?