If you are in the business of selling derivatives you have to value them from time to time, because counterparties want to know what their thing is worth, and regulators want to know how deep in the hole you are. This is not always as easy as valuing a stock by just going out and getting a quote. But the principles can be stated sort of simply: you just take an integral of your net discounted cash flows over every possible future state of the world, appropriately probability weighted.*
Easy to say, but hard to do, because you have only so much direct access to possible future states of the world. Fortunately there are rules of thumb for this, of greater or lesser reliability, which exclude the unlikely and immaterial states of the world (your BAC warrants are worth zero if the world ends this Friday, but that’s unlikely; you’re perhaps equally likely to eat a bacon bowl or a salad for lunch tomorrow, but your choice will have only an immaterial effect on the value of your BAC warrants). All of these methods, however, provide only market-sanctioned guesses about the fair value of your derivatives; if the future world moves in ways not contemplated by the moving parts of your model your calculations are just wrong.
This is, I’ve always thought, a nice way to think of the world, and certainly more conceptually satisfying than “it’s worth what people will pay for it” or “it’s worth what the formula says.” And once you get into thinking of things this way, you can have fun thinking of all the possible things that (1) are not trivially unlikely and (2) would have a not trivial effect on your stuff.
Like, it turns out, your own demise. Read more »









