Banks and other credit issuers took it on the chin this week with growing uncertainty in the credit markets. Citibank is down over 4% for the week while the S&P Global Financials Sector Index is down 4% over the past two weeks. The news of continuing declines in housing fueled worries that the broader credit markets would be damaged by a growing rate of sub-prime mortgage defaults and foreclosures. Wednesday, the National Association of Realtors reported that existing home sales fell more than expected by 3.8% in June to a seasonally adjusted annual rate of 5.75 million units, the lowest level since November 2002. Yesterday the Commerce Department reported that new-home purchases in June fell by 6.6%, the most since January.