THIS ought to have been a good week for the American economy. The country’s leaders at last ended a ludicrously irresponsible bout of fiscal brinkmanship, removing the threat of global financial Armageddon by agreeing to raise the federal debt ceiling. Yet far from heaving a sigh of relief, investors are nervous. Stockmarkets around the world have tumbled (see article). On August 2nd, the day the debt deal was signed, the S&P 500 index saw its biggest one-day fall in over a year, and yields on ten-year Treasury bonds dropped to 2.6%, their lowest level in nine months, as investors sought safety.