53 Pa. C.S. § 8169
(a) Net interest cost.--Net interest cost may be determined by using either the street method or the present worth method whichever method shall be specified in the official notice of sale.
(b) Street method.--Under the street method, a dollar amount shall be determined by computing the total amount of interest payable over the life of the series to stated maturity dates or earlier mandatory call dates and subtracting therefrom the amount of any premium paid above the aggregate principal amount of the bonds or notes or adding thereto the amount of any discount lawfully allowed in the sale.
(c) Present worth method.--Under the present worth method there shall be ascertained the semiannual rate, compounded semiannually, necessary to discount to present worth as of the date of the bonds or notes, the amounts payable on each interest payment date and on each stated maturity or earlier mandatory redemption date so that the aggregate of such amounts will equal the purchase price offered therefor exclusive of interest accrued to the date of delivery. The net interest cost shall be stated in terms of an annual percentage rate and shall be that rate of interest which is twice the semiannual rate so ascertained.
(d) Net interest rate.--The net interest rate for a series sold under the present worth method shall be the rate of the net interest cost. For a series sold under the street method, the net interest rate shall be determined by dividing the net interest cost by the product of $1,000 multiplied by the number of bond years from the date of the bonds or notes to the stated maturity or earlier mandatory call dates. A bond year shall be one full year that $1,000 of principal amount shall be outstanding and less than full years shall be fractionalized on a 360-day year basis.
53 Pa.C.S. § 8169