The issue presented is whether the county excise board [Board] is required by the introductory paragraph of 19 O.S.Supp. 1982 § 180.63 1 to grant class “A” officers the maximum salary increase allowable by the valuation-based portion of the formula in part A of that section. We answer in the negative and hold that, in the absence of a showing of arbitrary conduct on the part of the Board, a court may not interfere with the Board’s exercise of discretion in deciding what portion of the salary increase to be computed by the valuation-based formula in § 180.63(A) should be appropriated.
In a mandamus proceeding the plaintiffs, class “A” officers of McCurtain County [officers], sought an order directing the Board to grant them the maximum salary increase allowable by the valuation-based formula in § 180.63(A). The officers claimed that each of them was entitled to a salary of $25,740 qua class “A” officer. This sum, they urged, represents (a) a base salary of $18,790 [19 O.S.Supp.1982 § 180.-*93262(A)(5)]; (b) a salary increase of $450 under the terms of 19 O.S.Supp.1982 § 180.63(B) (population-based portion of the formula); and (c) a salary increase of $6,500 under the provisions of 19 O.S.Supp. 1982 § 180.63(A). The statutory salary increase of $6,500 was the focus of the controversy. The Board granted only a portion of the total amount because it considered the salary increase to be permissive and discretionary. Viewing the contested $6,500 differential as statutorily mandated, the district court ordered that, effective July 1, 1983, the sum of $25,740 be appropriated as the annual salary of every class “A” officer in the county.
We declare that the Board’s power over the level of a § 180.63(A) [valuation-based] increase is discretionary and reverse the trial court’s judgment.
The trial court’s decision to compel the Board to grant the higher salaries was based on two factors: (a) its interpretation of the introductory part of § 180.63 as mandating the maximum increase in the valuation-based portion and (b) its finding that funds were available to meet the maximum compensation level allowable by the statute under consideration.
The Board argues its authority to grant the increase in contest is discretionary because the language used in the introductory paragraph of the section clearly is permissive and not mandatory. The officers assert that the statute unmistakably indicates a legislative intent not to invest the Board with any discretion in computing incremental increases. They contend that when the introductory part is read together with part B of the statute, the only conclusion to be reached is that the Board’s duty to grant the salary increases — based on the formulae in parts A and B of § 180.63 — is mandatory.
The goal of statutory construction is to follow the intent of the legislature.2 Statutory words are to be understood in their ordinary sense, except when a contrary intention plainly appears.3 To ascertain legislative intent we look to the language of the pertinent statute.
The terms of 19 O.S.Supp.1982 § 180.63 provide in pertinent part:
“In every county in this state, the salary of all county officers named in groups ‘A’ and ‘B’ may be increased from the applicable basic salary named in Section 180.62 of this title, for net valuation or serviceability, according to the following scale: [emphasis added]
A. To the basic salary: [the text that follows here sets out the valuation-based part of the formula]
* * * * * *
B. And also the salary of each county officer shall be additionally increased from the basic salary named in Section 180.62 of this title, and the additions thereto heretofore provided in this section, for population or service load according to the following scale: * * * [emphasis added]
Whether the introductory part of § 180.63 makes the valuation-based increase provided in part A mandatory depends on the meaning to be ascribed to the legislature’s use of the word “may”. Extant case law often held that “may” usually denotes “permissive or discretional, and not mandatory, action or conduct”,4 while “shall” is usually given its common meaning of “must”, implying a command or mandate.5 *933On rare occasions indeed has this court declared that “may” could be taken as synonymous with “shall”. When it did so it was because to divine otherwise from the context of the enactment under review would “defy fundamental logic” and “defeat the purpose and intent of the statute”.6
We think the word “may” in the introductory part of § 180.63 was used to convey its ordinary meaning and signifies permissive rather than mandatory action. This construction neither defies logic nor defeats the statute’s purpose. Firstly, parts A and B provide for separate and distinct factors for increasing the base salary. The increase in part A is based upon the valuation of county property while that in part B is geared to the service load measured by the county’s population. There is no logical basis for construing the salary increase provided for in these two parts to be mandatory simply because they were placed in separate paragraphs within the same statute. If the legislature had intended that the mandatory “shall”, found in part B, apply also to part A, it would have been a simple matter to have employed that word instead of “may” in the introductory paragraph of the section. Further support for this view is found in the fact that prior to 1972 the language in the introductory part provided that salaries “shall be increased”.7 It was in 1972 that the word “shall” was changed to “may”.8 It has since then remained unaltered through five successive amendments. If the legislature had intended for the valuation-based portion of the salary increase formula in part A to be mandatory, it would not have changed the wording of the introductory paragraph from “shall” to “may”, while still retaining the mandatory “shall” in part B. From our examination of the antecedent legislation, viewed in conjunction with the enactment here under review,9 we conclude that the word “may”, as it appears in the introductory part, was intended to make the valuation-based portion of the salary increase permissive.
We also hold that there was no basis in law or in fact for the trial judge’s finding that funds were available for the salary increases. The present statutory scheme for controlling county budgets reposes authority in the Board to allocate available revenues among the budgets proposed by competing county officers and to reduce budget items that are in excess of needs.10 Funds that have been apportioned under the Board’s allocation formula are not “available” for any other purpose. Because the Board has sole discretionary power to allocate revenues, its action in reducing any permissible item in an officer’s estimate of needs is presumed to be correct until overcome by a showing of arbitrary conduct on the part of the Board.11
*934The maximum level allowable under the valuation-based portion of the salary increase is not mandated by law. Arbitrariness in the Board’s budget allocation was neither alleged nor shown. There was hence error in allowing the officers’ claim for recovery on the theory that, because the Board had at its disposal sufficient money to fund the maximum authorized salary level, mandamus lay to compel the increased salary appropriation sought.
The trial court’s judgment is reversed.
SIMMS, C.J., and LAVENDER, HAR-GRAVE, WILSON and KAUGER, JJ., concur. DOOLIN, V.C.J., and HODGES and SUMMERS, JJ., dissent.. The pertinent part of § 180.63 is set forth later in the opinion.
. Independent School Dist. No. 89 of Oklahoma County v. Oklahoma City Federation of Teachers, Local 2309 of American Federation of Teachers, Okl., 612 P.2d 719, 721 [1980]; J.S. Bryan & Sons v. Vernor, 172 Okl. 382, 45 P.2d 468, 470 [1935],
. 25 O.S.1981 § 1.
. Shea v. Shea, Okl., 537 P.2d 417, 418 [1975]; see also, State ex rel. Cartwright v. Oklahoma Natural Gas Co., Okl., 640 P.2d 1341, 1345 [1982]; State ex rel. Dept. of Transportation v. Moss, Okl., 602 P.2d 638, 640 [1979]; Assoc. of Classroom Teachers of Oklahoma City, Inc. v. Independent School Dist. No. 89, Okl., 540 P.2d 1171, 1176 [1975]; Clark v. Miller, Okl.App., 631 P.2d 1343, 1345 [1981],
.Sneed v. Sneed, Okl., 585 P.2d 1363, 1364 [1978]; Oldham v. Drummond Board of Education of Independent School Dist. No. 1-85, Okl., 542 P.2d 1309, 1311 [1975]; Oklahoma Alcoholic *933Beverage Control Bd. v. Moss, Okl., 509 P.2d 666, 668 [1973],
. Assoc, of Classroom Teachers of Oklahoma City, Inc. v. Independent School Dist. No. 89, supra note 4 at 1176; State ex rel. Board of Education of City of Tulsa v. Morley, 168 Okl. 259, 34 P.2d 258, 266 [1934],
. 19 O.S.1971 § 180.63.
. Okl.Sess.Laws 1972, c. 115, § 1, p. 137.
. Antecedent legislative enactments, which have been repealed or superseded, may be resorted to and considered in the construction of amend-atory acts in pari materia. Letteer v. Conservancy District No. 30, Okl., 385 P.2d 796, 800 [1963],
. 68 O.S.1981 § 2487; Summey v. Tisdale, Okl., 658 P.2d 464, 468-469 [1982]; Excise Board of Greer County v. Rogers, Okl., — P.2d-[56 O.B.J. 37, Sup.Ct.No. 59,259, December 26, 1984],
.Summey v. Tisdale, supra note 10 at 469; Excise Board of Greer County v. Rogers, supra note 10.
The trial court’s reliance on Neel v. Board of County Commissioners of Cherokee County, Okl., 617 P.2d 201, 204 [1980], in support of its decision that the Board could not refuse salary requests when revenue is sufficient to meet the requests, is misplaced. In Neel we held that county excise boards were not authorized to reduce budgeted items when adequate funding was available. This holding was based in part upon 68 O.S.1971 § 2487, which, at that time, did not empower county excise boards to delete items considered in estimates of needs. The scheme for controlling county budgets came to be amended in 1979. The new statutory regime now in force grants county excise boards the *934authority to examine estimates of needs and to eliminate requests in excess of needs. 68 O.S. 1981 § 2487.