our non-operating investment activity resulted in net losses of $ 12.7 million in 2009 and $ 52.3 million in 2008 . the improvement of nearly $ 40 million is primarily attributable to a reduction in the other than temporary impairments recognized on our investments in sponsored mutual funds in 2009 versus 2008 . the following table details our related mutual fund investment gains and losses ( in millions ) during the past two years. .
what percentage of the net inflows primarily from institutional investors was due to the transfer from retirement funds to target-date trusts?
lower income of $ 16 million from our money market holdings due to the significantly lower interest rate environment offset the improvement experienced with our fund investments . there is no impairment of any of our mutual fund investments at december 31 , 2009 . the 2009 provision for income taxes as a percentage of pretax income is 37.1% ( 37.1 % ) , down from 38.4% ( 38.4 % ) in 2008 and .9% ( .9 % ) lower than our present estimate of 38.0% ( 38.0 % ) for the 2010 effective tax rate . our 2009 provision includes reductions of prior years 2019 tax provisions and discrete nonrecurring benefits that lowered our 2009 effective tax rate by 1.0% ( 1.0 % ) . 2008 versus 2007 . investment advisory revenues decreased 6.3% ( 6.3 % ) , or $ 118 million , to $ 1.76 billion in 2008 as average assets under our management decreased $ 16 billion to $ 358.2 billion . the average annualized fee rate earned on our assets under management was 49.2 basis points in 2008 , down from the 50.2 basis points earned in 2007 , as lower equity market valuations resulted in a greater percentage of our assets under management being attributable to lower fee fixed income portfolios . continuing stress on the financial markets and resulting lower equity valuations as 2008 progressed resulted in lower average assets under our management , lower investment advisory fees and lower net income as compared to prior periods . net revenues decreased 5% ( 5 % ) , or $ 112 million , to $ 2.12 billion . operating expenses were $ 1.27 billion in 2008 , up 2.9% ( 2.9 % ) or $ 36 million from 2007 . net operating income for 2008 decreased $ 147.9 million , or 14.8% ( 14.8 % ) , to $ 848.5 million . higher operating expenses in 2008 and decreased market valuations during the latter half of 2008 , which lowered our assets under management and advisory revenues , resulted in our 2008 operating margin declining to 40.1% ( 40.1 % ) from 44.7% ( 44.7 % ) in 2007 . non-operating investment losses in 2008 were $ 52.3 million as compared to investment income of $ 80.4 million in 2007 . investment losses in 2008 include non-cash charges of $ 91.3 million for the other than temporary impairment of certain of the firm 2019s investments in sponsored mutual funds . net income in 2008 fell 27% ( 27 % ) or nearly $ 180 million from 2007 . diluted earnings per share , after the retrospective application of new accounting guidance effective in 2009 , decreased to $ 1.81 , down $ .59 or 24.6% ( 24.6 % ) from $ 2.40 in 2007 . a non-operating charge to recognize other than temporary impairments of our sponsored mutual fund investments reduced diluted earnings per share by $ .21 in 2008 . investment advisory revenues earned from the t . rowe price mutual funds distributed in the united states decreased 8.5% ( 8.5 % ) , or $ 114.5 million , to $ 1.24 billion . average mutual fund assets were $ 216.1 billion in 2008 , down $ 16.7 billion from 2007 . mutual fund assets at december 31 , 2008 , were $ 164.4 billion , down $ 81.6 billion from the end of 2007 . net inflows to the mutual funds during 2008 were $ 3.9 billion , including $ 1.9 billion to the money funds , $ 1.1 billion to the bond funds , and $ .9 billion to the stock funds . the value , equity index 500 , and emerging markets stock funds combined to add $ 4.1 billion , while the mid-cap growth and equity income stock funds had net redemptions of $ 2.2 billion . net fund inflows of $ 6.2 billion originated in our target-date retirement funds , which in turn invest in other t . rowe price funds . fund net inflow amounts in 2008 are presented net of $ 1.3 billion that was transferred to target-date trusts from the retirement funds during the year . decreases in market valuations and income not reinvested lowered our mutual fund assets under management by $ 85.5 billion during 2008 . investment advisory revenues earned on the other investment portfolios that we manage decreased $ 3.6 million to $ 522.2 million . average assets in these portfolios were $ 142.1 billion during 2008 , up slightly from $ 141.4 billion in 2007 . these minor changes , each less than 1% ( 1 % ) , are attributable to the timing of declining equity market valuations and cash flows among our separate account and subadvised portfolios . net inflows , primarily from institutional investors , were $ 13.2 billion during 2008 , including the $ 1.3 billion transferred from the retirement funds to target-date trusts . decreases in market valuations , net of income , lowered our assets under management in these portfolios by $ 55.3 billion during 2008 . management 2019s discussion & analysis 21 .