pre_text: mortgage banking activities the company enters into commitments to originate loans whereby the interest rate on the loan is determined prior to funding . these commitments are referred to as interest rate lock commitments ( 201cirlcs 201d ) . irlcs on loans that the company intends to sell are considered to be derivatives and are , therefore , recorded at fair value with changes in fair value recorded in earnings . for purposes of determining fair value , the company estimates the fair value of an irlc based on the estimated fair value of the underlying mortgage loan and the probability that the mortgage loan will fund within the terms of the irlc . the fair value excludes the market value associated with the anticipated sale of servicing rights related to each loan commitment . the fair value of these irlcs was a $ 0.06 million and a $ 0.02 million liability at december 31 , 2007 and 2006 , respectively . the company also designates fair value relationships of closed loans held-for-sale against a combination of mortgage forwards and short treasury positions . short treasury relationships are economic hedges , rather than fair value or cash flow hedges . short treasury positions are marked-to-market , but do not receive hedge accounting treatment under sfas no . 133 , as amended . the mark-to-market of the mortgage forwards is included in the net change of the irlcs and the related hedging instruments . the fair value of the mark-to-market on closed loans was a $ 1.2 thousand and $ 1.7 million asset at december 31 , 2007 and 2006 , respectively . irlcs , as well as closed loans held-for-sale , expose the company to interest rate risk . the company manages this risk by selling mortgages or mortgage-backed securities on a forward basis referred to as forward sale agreements . changes in the fair value of these derivatives are included as gain ( loss ) on loans and securities , net in the consolidated statement of income ( loss ) . the net change in irlcs , closed loans , mortgage forwards and the short treasury positions generated a net loss of $ 2.4 million in 2007 , a net gain of $ 1.6 million in 2006 and a net loss of $ 0.4 million in 2005 . credit risk credit risk is managed by limiting activity to approved counterparties and setting aggregate exposure limits for each approved counterparty . the credit risk , or maximum exposure , which results from interest rate swaps and purchased interest rate options is represented by the fair value of contracts that have unrealized gains at the reporting date . conversely , we have $ 197.5 million of derivative contracts with unrealized losses at december 31 , 2007 . the company pledged approximately $ 87.4 million of its mortgage-backed securities as collateral of derivative contracts . while the company does not expect that any counterparty will fail to perform , the following table shows the maximum exposure associated with each counterparty to interest rate swaps and purchased interest rate options at december 31 , 2007 ( dollars in thousands ) : counterparty credit .
post_text: .
table: Counterparty Credit Risk
table: Bank of America $48,161
table: Lehman Brothers 29,136
table: JP Morgan 18,878
table: Union Bank of Switzerland 15,562
table: Credit Suisse First Boston 11,047
table: Royal Bank of Scotland 6,164
table: Morgan Stanley 2,215
table: Salomon Brothers 1,943
table: Total exposure $133,106
question: Analyse this data from a financial earnings document. what percentage of counterparty exposure at december 31 2007 is represented by union bank of switzerland?