Investment banks: Guesstimate Sachs

Estimates of what Wall Street might earn this year were already rosy. With the credit markets taking another turn for the worse, they were starting to look downright silly. So analysts are rightly, if belatedly, slashing forecasts. Even so, divining just how much coin investment banks will mint is still a crapshoot. Sure, working out writedowns has become de rigeur practice. But it’s more art than science. Take Goldman Sachs, whose chief, Lloyd Blankfein, steered it to record results in 2007. O...