the fair value of our total investments increased $ 4.8 billion during 2010 , primarily due to unrealized appreciation , the inves- ting of operating cash flows , and the portfolios acquired in the 2010 corporate acquisitions . the following tables show the market value of our fixed maturities and short-term investments at december 31 , 2010 and 2009 . the first table lists investments according to type and the second according to s&p credit rating. .