. in addition , the amount representing the credit-related portion of otti on available for sale securities would reduce our earnings and regulatory capital ratios . the expected weighted-average life of investment securities ( excluding corporate stocks and other ) was 4.0 years at december 31 , 2012 and 3.7 years at december 31 , 2011 . we estimate that , at december 31 , 2012 , the effective duration of investment securities was 2