Conventional wisdom says that it is better to be a large company than a small one when credit is tight. Bigger firms have more room for maneuver(机动):They have access to more types of funding, they have more fat to cut, and they have greater bargaining power with lenders. Even so, life is getting ever more uncomfortable for the bigger beasts of the corporate jungle.According to the Federal Reserve’s most recent lending survey, American banks are tightening terms more aggressively for bigger firms than for smaller ones. Lenders are more cautious than theyhave been at least since 1990. The story among European banks is similar. Lenders in emerging markets can be more suspicious of multinational firms than they are of locals. "We just don’t know what they’ve got on their balance-sheets back home," says one bank boss in Africa.Violent movements in exchange rates are causing additional headaches, says Andrew Balfour of Slaughter & May, a law firm. Calculations of financial ratios can be thrown out by wild currency movements, potentially triggering breaches of loan agreements. Companies with sterling-denominated credit lines may find that their facilities are not big enough as a result of the pound’s recent sharp fall, for instance.It is not panic stations yet. Most firms can survive for a while with the credit tap turned off. Analysis by Moody’s, a rating agency, shows that the vast majority of highly rated companies in America and Europe have enough headroom, in the form of cash and undrawn bank facilities, to be able to survive for 12 months without needing new financing. European corporate-debt markets have seen a rare flurry(惊慌) of issues in the past few days by opportunistic, highly rated firms.Governments are also working hard to prop up credit markets. The Fed’s program to buy commercial paper, a form of short-term company debt, had acquired almost ＄300 billion by November 26th. Banks on both sides of the Atlantic are issuing lots of government-backed bonds, which should encourage lending. It is believed to be easier for bigger companies during the tight period, for they have larger space for （）.