(3) Securities Investment Securities The amortized cost and fair values of investment securities are as follows (in thousands): December 31, Amortized Fair Gross Unrealized Amortized Fair Gross Unrealized Cost Value Gain Loss Cost Value Gain Loss U.S. Treasury $ 7982 °$ 7,981 $= (6) $ = $ = geh = Municipal and other tax-exempt 222,195 223,487 2,634 (1,342) 207,177 207,641 1,847 (1,383) Mortgage-backed U.S. agency Securities 7,381 7,620 240 (68) 11,541 11,567 64 (38) Other debt securities 3,555 3,540 - (15) 14,653 14,659 6 ~ $233,371. $233,867 $1,917 $(1.421) Total $241,113. $242,628 $2,874 $11,359) The amortized cost and fair values of investment securities at December 31, 2001, by contractual maturity, are as shown in the following table (dollars in thousands): During 2000, BOK Financial sold a mortgage-backed security with a remaining amortized cost of $175 thousand. The acquisition cost of this security was $4.9 million. Therefore, these sales were permitted under the sales deemed to be.at maturity provisions of Statement of Financial Accounting Standards No. 115, “Accounting for Certain Investments in Debt and Equity Securities.” Weighted Less than One to Five to Over Average One Year Five Years Ten Years Ten Years Total Maturity? U.S. Treasuries: Amortized cost $7,982 $ - $ - = $ 7,982 0.10 Fair value 7,981 - - - 7,981 Nominal yield 1.59% - = - 1.59% Municipal and other tax-exempt: Amortized cost $60,046 $125,197 $35,047 $1,905 $222,195 2.77 Fair value 60,146 126,364 35,119 1,858 223,487 Nominal yield! 6.81% 7.05% 7.72% 9.38% 711% Other debt securities: Amortized cost $ . 346 $ 3,034 $ 125 $50 $3,555 2.86 Fair value 346 3,034 116 44 3,540 Nominal yield 1.52% 5.42% 7.00% 7.00% 5.12% Total fixed maturity securities: Amortized cost $68,374 $128,231 $35,172 $1,955 $233,732 2.68 Fair value 68,473 129,398 35,235 1,902 235,008 Nominal yield 6.17% 7.01% 7.72% 9.32% 6.89% Mortgage-backed ‘securities: ; Amortized cost $7,381 = Fair value 7,620 Nominal yield? 6.74% Total investment securities: Amortized cost $241,113 Fair value 242,628 6.89% Nominal yield 1 Calculated ona taxable equivalent basis using a 39% effective tax rate. 2 The average expected lives of mortgage-backed securities were 0.54 years based upon current prepayment assumptions. >The nominal yield on mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. ‘Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty.