If there’s any doubt America faces its gravest financial crisis in decades, consider this sobering evidence: Pension plans for some of the 1,500 largest U.S. companies have lost about $280 billion so far this year. In November alone, pension plans lost about $130 billion, marking the second consecutive month of record declines, according to a new report from Mercer, the financial consulting firm. The companies Mercer studied — those in the Standard & Poor’s 1,500 index, which includes household names like 3M and Coca Cola — reported their pension plans ended 2007 with a $60 billion surplus. So the swiftness of this year’s decline is astonishing. (Read «Is It OK to Pray for Your 401(k)?»)