average securities purchased under resale agreements increased to $ 4.69 billion for the year ended december 31 , 2011 from $ 2.96 billion for the year ended december 31 , 2010 . average trading account assets increased to $ 2.01 billion for the year ended december 31 , 2011 from $ 376 million for 2010 . averages benefited largely from an increase in client demand associated with our trading activities . in connection with these activities , we traded in highly liquid fixed-income securities as principal with our custody clients and other third- parties that trade in these securities . our average investment securities portfolio increased to $ 103.08 billion for the year ended december 31 , 2011 from $ 96.12 billion for 2010 . the increase was generally the result of ongoing purchases of securities , partly offset by maturities and sales . in december 2010 , we repositioned our portfolio by selling approximately $ 11 billion of mortgage- and asset-backed securities and re-investing approximately $ 7 billion of the proceeds , primarily in agency mortgage-backed securities . the repositioning was undertaken to enhance our regulatory capital ratios under evolving regulatory capital standards , increase our balance sheet flexibility in deploying our capital , and reduce our exposure to certain asset classes . during 2011 , we purchased $ 54 billion of highly rated u.s . treasury securities , federal agency mortgage-backed securities and u.s . and non-u.s . asset-backed securities . as of december 31 , 2011 , securities rated 201caaa 201d and 201caa 201d comprised approximately 89% ( 89 % ) of our portfolio , compared to 90% ( 90 % ) rated 201caaa 201d and 201caa 201d as of december 31 , 2010 . loans and leases averaged $ 12.18 billion for the year ended december 31 , 2011 , compared to $ 12.09 billion for 2010 . the increases primarily resulted from higher client demand for short-duration liquidity , offset in part by a decrease in leases and the purchased receivables added in connection with the conduit consolidation , mainly from maturities and pay-downs . for 2011 and 2010 , approximately 29% ( 29 % ) and 27% ( 27 % ) , respectively , of our average loan and lease portfolio was composed of short-duration advances that provided liquidity to clients in support of their investment activities related to securities settlement . the following table presents average u.s . and non-u.s . short-duration advances for the years indicated: .
what portion of the total short-term duration advances are u.s short-term advances?
for the year ended december 31 , 2011 , the increase in average non-u.s . short-duration advances compared to the prior-year period was mainly due to activity associated with clients added in connection with the acquired intesa securities services business . average other interest-earning assets increased to $ 5.46 billion for the year ended december 31 , 2011 from $ 1.16 billion for 2010 . the increase was primarily the result of higher levels of cash collateral provided in connection with our role as principal in certain securities borrowing activities . average interest-bearing deposits increased to $ 88.06 billion for the year ended december 31 , 2011 from $ 76.96 billion for 2010 . the increase reflected client deposits added in connection with the may 2010 acquisition of the intesa securities services business , and higher levels of non-u.s . transaction accounts associated with new and existing business in assets under custody and administration . average other short-term borrowings declined to $ 5.13 billion for the year ended december 31 , 2011 from $ 13.59 billion for 2010 , as the higher levels of client deposits provided additional liquidity . average long-term debt increased to $ 8.97 billion for the year ended december 31 , 2011 from $ 8.68 billion for the same period in 2010 . the increase primarily reflected the issuance of an aggregate of $ 2 billion of senior notes by us in march 2011 , partly offset by the maturities of $ 1 billion of senior notes in february 2011 and $ 1.45 billion of senior notes in september 2011 , both previously issued by state street bank under the fdic 2019s temporary liquidity guarantee program . additional information about our long-term debt is provided in note 9 to the consolidated financial statements included under item 8. .