JPMorgan Chase & Co., the second-biggest American bank, said the value of a $1.2 billion investment in Freddie Mac and Fannie Mae shares has declined by half so far this quarter. The losses from the investment in perpetual preferred shares of the two American mortgage lenders may cut into quarterly earnings, the company said yesterday in a regulatory filing. Freddie and Fannie preferred stock is trading as low as 19 cents on the dollar on speculation the companies may suspend dividends to weather the biggest housing slump since the Great Depression. “The precise amount of losses that may be incurred on these securities for the third quarter is difficult to determine, given the significant volatility being experienced in the market values of these securities,” JPMorgan said in the SEC filing.