????债务上限的千年虫危机

????据很多交易员称，华尔街的计算机系统通过自动程序将美国政府的利息支付转给债券持有人。甚至可能在这些资金尚未到账的情况下。不同于其他债券，这些计算机没有设计程序先检查支付资金，因为每个人都假定美国政府会按时付款。这下糟了。

????如果美国政府停止支付，大银行可能得拿出自己的现金来支付这些并不属于它们的债务的利息。这可能造成一些交易商远离美国国债市场，让美国国债交易更为困难。或者，它可能占据银行体系资金，导致银行难以进行借贷和交易。

????另外一个问题：交易员利用美国国债为衍生品和其他交易提供融资。通常情况下，美国国债的利息可以覆盖这些交易相当一部分的持有成本。支付转移也被设置为自动完成。因此，美国政府违约可能导致其他很多交易员自动违约，触发可能造成各个市场暴跌的抛盘浪潮。结果将是一片混乱。

????Debt ceiling's Y2K-like problem

????According to a number of traders, Wall Street's computer systems are programmed to automatically pass along U.S. government payments to bond holders. Even, perhaps, if those payments aren't made. Unlike other bonds, the computers aren't coded to check for the payments first, because everyone assumed Uncle Sam would always pay on time. Oops.

????If the government stops making payments, big banks could be shelling out their own cash to pay interest on debt that's not theirs. That could cause some dealers to back away from the Treasury market, making it harder to trade U.S. debt. Or it could just be a drain on the banking system, making it difficult for banks to lend and trade.

????Another problem: Traders leverage Treasury bonds to finance derivative bets and other transactions. Often the interest on Treasuries covers much of the carrying cost of those trades. And the transfers of payments are set up to be automatic as well. So a government default could lead lots of other traders to automatically default, triggering a wave of selling that could cause a variety of markets to tumble. It would be a mess.