Guardian: The value of BP has fallen by £20bn since the disaster in the Gulf of Mexico a fortnight ago, or by about twice as much as the current steepest estimate of the eventual clean-up bill. Has the market over-reacted? The bald financial facts suggest so. BP shares, at 558p, yield 6.5% and few analysts think the dividend could be cut as a result of the catastrophe. Even if the cost to BP were £10bn, all the cash would not depart at once; BP also has scope to borrow. And, with the price of oil at …