China’s Dagong Global Credit Rating cut its credit rating for United States debt by one notch to A-minus from A on Thursday, saying an agreement reached by Congress to raise the government’s borrowing ceiling failed to address the root cause of its debt issue. Should investors care? In theory the answer is yes, as China is a large holder of US Treasuries. If Chinese officials were to take this downgrade seriously, they may end up trimming China’s holdings of US Treasuries, causing a market sell off. In practice however, the answer is no, for four reasons. First, it is very...