From Bloomberg:The U.S. commercial paper market shrank for a third week, extending the biggest slump in at least seven years, as investors balked at buying short-term debt backed by mortgage assets.Asset-backed commercial paper, which accounted for half the market, tumbled $59.4 billion to $998 billion in the week ended yesterday, the lowest since December, according to the Federal Reserve. Total short-term debt maturing in 270 days or less fell $62.8 billion to a seasonally adjusted $1.98 trillion.Commercial paper outstanding has fallen $244.1...