“Last month’s announcement on Shell’s reserves outraged shareholders and knocked more than $15bn off its stock market value as investors contemplated less than 11 years of reserves at current output rates against more than 13 before the downgrade.”
(Though of course calculating reserves depends on current price, technology, profitability, geological uncertainties, etc., so this isn’t quite the same as saying, ‘well, now we have 11 billion tons instead of 13 billion’; nonetheless, 11 years?)