Plaintiff served on the North Carolina Utilities Commission (NCUC) from 1 January 1970 to 30 April 1975 and from 1 July 1977 through 17 August 1979. During his tenure at the NCUC, plaintiff was a member of the Teachers’ and State Employees’ Retirement System of North Carolina (TSERS).
Plaintiff served as a judge on the North Carolina Court of Appeals from 29 August 1979 to 30 June 1994. During his tenure at the Court of Appeals, plaintiff was a member of the Consolidated Judicial Retirement System of North Carolina (CJRS).1 His judicial retirement benefits vested in August 1984, following five years of creditable service. Upon his retirement from the judiciary in 1994, plaintiff applied for and received a judicial service retirement allowance from the CJRS for the month of July 1994.
In July 1994 the Governor of North Carolina appointed plaintiff as Chair of the NCUC. As a result of this appointment, plaintiff again received a monthly salary from the State of North Carolina and again became a member of the TSERS. Plaintiff’s monthly CJRS retirement *315allowance was suspended from August 1994 through December 1996 during his service as Chair of the NCUC. On 31 December 1996 plaintiff resigned from the NCUC, and his CJRS retirement allowance was restored effective 1 January 1997.
On 30 September 1997 plaintiff brought suit against the CJRS, the Board of Trustees of the TSERS (Board), and the State of North Carolina on the ground that he was entitled to receive his monthly retirement allowance under the CJRS while he was earning a salary as Chair of the NCUC and contributing to the TSERS. On 5 June 1998 an administrative law judge determined that plaintiffs judicial retirement allowance was properly suspended while he worked at the NCUC. On 4 August 1998 the Board accepted that recommendation and entered its final agency decision. On 29 March 1999 the trial court affirmed the final agency decision and entered summary judgment in favor of defendants.
On 7 March 2000, the Court of Appeals, in a split decision, affirmed the trial court. Wells v. Consolidated Jud’l Ret. Sys. of N.C., 136 N.C. App. 671, 526 S.E.2d 486 (2000). The Court of Appeals held that the Board properly suspended plaintiff’s retirement allowance for the period of time he served as Chair of the NCUC. Id. at 677, 526 S.E.2d at 491. The majority based its decision on an interpretation of the interplay of several statutes elaborating the TSERS and the CJRS. Id. at 673-77, 526 S.E.2d at 488-91. Judge Horton dissented on the grounds that the “restored to service” provision in Article 1 of the Retirement System applied only to retirees under the TSERS and could not be applied to plaintiff, a retiree under the CJRS. Id. at 678, 526 S.E.2d at 491 (Horton, J., dissenting).
The General Assembly codified the Retirement System within Chapter 135 of the General Statutes of North Carolina. Chapter 135, entitled “Retirement System for Teachers and State Employees; Social Security; Health Insurance Program for Children,” incorporates, among other things, both the TSERS in Article 1 and the CJRS in Article 4. The General Assembly enacted Article 1 in 1941 and Article 4 in 1974. Because this case turns upon the interpretation of and interplay among sections within Chapter 135, it is instructive to set out preliminarily the provisions of the CJRS in Article 4 and the *316TSERS in Article 1 relevant to our inquiry.2 At the time plaintiff retired and received his first judicial retirement check under the CJRS, Article 4 provided in pertinent part:
The retirement benefits of any person who becomes a justice or judge on or after January 1, 1974, shall be determined solely in accordance with the provisions of this Article.
N.C.G.S. § 135451(c) (1981). Also, section 135-71 of Article 4 provided at that time:
In the event that a retired former member should at any time return to service as a justice or judge, his retirement allowance shall thereupon cease and he shall be restored as a member of the Retirement System.
N.C.G.S. § 135-71(a) (1981). At the time plaintiffs benefits vested, Article 1 provided, in pertinent part:
Should a beneficiary who retired on an early or service retirement allowance be restored to service for a period of time exceeding six calendar months, his retirement allowance shall cease, he shall again become a member of the Retirement System and he shall contribute thereafter at the uniform contribution rate payable by all members.
N.C.G.S. § 135-3(8)(c) (Supp. 1983).
Our review of the statutory scheme leads us to conclude that the legislature anticipated the possibility that recipients under the Retirement System might return to active employment on behalf of the State of North Carolina. See N.C.G.S. § 135-3(8)(c) (Supp. 1983); N.C.G.S. § 135-71(a) (1981). If a former member of the TSERS is restored to service as an employee or teacher, N.C.G.S. § 135-3(8)(c) provides for the cessation or suspension of retirement benefits while the person contributes to the TSERS. The retirement allowance of a former member of the CJRS who returns to active judicial service is likewise suspended under N.C.G.S. § 135-71.
The narrow question presented by this appeal is whether plaintiffs monthly CJRS retirement allowance was properly suspended *317during his active employment as Chair of the NCUC. Stated alternatively, the question is whether a contributing member of the TSERS can simultaneously draw a retirement allowance from the CJRS. We affirm the Court of Appeals and hold that the Board properly suspended plaintiffs retirement allowance during his service as Chair of the NCUC.
Section 135-52 makes the provisions of Article 1 applicable to the other articles in Chapter 135. N.C.G.S. § 135-52 (1981). That section provides in relevant part as follows:
References in Article 1 of this Chapter to the provisions of “this Chapter” shall not necessarily apply to . . . Article [4]. However, except as otherwise provided in this Article, the provisions of Article 1 are applicable and shall apply to and govern the administration of the Retirement System established hereby. Not in limitation of the foregoing, the provisions of G.S. 135-5(h), 135-5(n), 135-9, 135-10, 135-12 and 135-17 are specifically applicable to the Retirement System established hereby.
N.C.G.S. § 135-52(a) (1981)(emphasis added). This section mandates that the provisions of Article 1, including the “beneficiary return to service” provision of N.C.G.S. § 135-3(8)(c), affect the benefits of CJRS members who return to service as employees, “except as otherwise provided” by Article 4. Id.
Article 1, section 135-3(8) (c) prohibits simultaneous contribution into the TSERS and receipt from the Retirement System. N.C.G.S. § 135-3(8)(c) (Supp. 1983). An examination of Article 4 reveals no exception to that principle. Plaintiff argues that section 135-71 provides such an exception. That section contemplates only an individual’s return to service “as a justice or judge.” Section 135-3(8)(c), on the other hand, refers to all returning “beneficiaries.” “Beneficiary” is defined in section 135-1(6) as “any person in receipt of a pension, an annuity, a retirement allowance or other benefit as provided by this Chapter.” N.C.G.S. § 135-1(6) (1981) (emphasis added). The legislature tailored the language of section 135-71 to address only retired CJRS members returning as contributing members of the CJRS. In contrast, the language of section 135-3(8)(c) casts a wider net, applying broadly to all recipients of Retirement System benefits under Chapter 135 who return as contributors to the TSERS. N.C.G.S. § 135-3(8)(c) (Supp. 1983); N.C.G.S. § 135-71 (1981). Plaintiff fits squarely into this latter category.
*318Our interpretation of N.C.G.S. § 135-3(8)(c) is further strengthened by review of amendments to that section since 1984, when plaintiff’s entitlement to a retirement allowance vested. Later statutory amendments provide useful evidence of the legislative intent guiding the prior version of the statute. See Childers v. Parker’s, Inc., 274 N.C. 256, 260, 162 S.E.2d 481, 484 (1968) (an amended version of a statute may not necessarily be a departure from the old law but rather a clarification of what was previously intended). The present version of N.C.G.S. § 135-3(8)(c), recodified as Article 1, Section 135-3(8)(d), provides, in part, as follows:
Should a beneficiary who retired on an early or service retirement allowance under this Chapter be restored to service as an employee or teacher, then the retirement allowance shall cease as of the first of the month following the month in which the beneficiary is restored to service and the beneficiary shall become a member of the Retirement System and shall contribute thereafter as allowed by law at the uniform contribution payable by all members.
N.C.G.S. § 135-3(8)(d) (1999) (emphasis added). The addition of the words “under this Chapter” as a qualifier to “early or service retirement allowance” clarifies that this provision was intended to apply to each of the articles within Chapter 135.
Relying on Judge Horton’s dissent, plaintiff further argues that an interpretation of N.C.G.S. § 135-3(8)(c) that covers judges in Article 4 renders N.C.G.S. § 135-71 meaningless. Plaintiff argues that section 135-71, by its very terms, is an exception to section 135-3(8)(c), specifically directed only at members of the CJRS who return to service in a position included in the Chapter. See Wells, 136 N.C. App. at 682, 526 S.E.2d at 494 (Horton, J., dissenting).
Section 135-71 was intended to, and does, apply to one specification: when a retired member of the CJRS returns to active membership in the CJRS. Section 135-71 therefore effects a valid legislative purpose. The definitional precision of section 135-71 leaves no room for the inclusion of judges who elect to become contributing members of TSERS. Accordingly, section 135-71 does not act as the type of exception contemplated by section 135-52. Rather, N.C.G.S. § 135-3(8)(c) applies to Article 4 and prevents plaintiff from drawing a retirement allowance from the CJRS while contributing to the TSERS.
*319Plaintiff contends that the absence of N.C.G.S. § 135-3(8)(c) (designated as subsection (8)(d) in the 1994 version of the statute) from the list of six statutory provisions specifically referenced in N.C.G.S. § 135-52 indicates that the legislature intended N.C.G.S. § 135-3(8)(c) not to apply to Article 4. This interpretation is without merit because it ignores the words “not in limitation of,” which indicate that the list of specifically applicable provisions is not exclusive. N.C.G.S. § 135-52.
Plaintiff further contends that application of N.C.G.S. § 135-3(8)(c) to CJRS recipients is inconsistent with the requirement of N.C.G.S. § 135-51 that the retirement allowance of any judge be determined solely in accordance with the provisions of Article 4. N.C.G.S. § 135-51(c). According to plaintiff, this inconsistency provides an exception to section 135-52. We disagree. The suspension of a monthly retirement allowance when a retiree again becomes a contributing member of the Retirement System is not inconsistent with Article 4. Service retirement benefits under the CJRS were, and still are, determined in accordance with sections 135-58 and 135-71(b) of Article 4. N.C.G.S. § 135-58 (1981 & 1999); N.C.G.S. § 135-71(b) (1981 & 1999).
We emphasize that the agency established to administer the retirement statutes has adhered to the same interpretation on this matter since the 1970s, which was corroborated in the deposition of Timothy Bryan, Deputy Director of the Retirement Systems Division of the Department of State Treasurer. See, e.g., Thornburg v. Consolidated Jud’l Ret. Sys. of N.C., 137 N.C. App. 150, 150-51, 527 S.E.2d 351, 352 (2000) (observing suspension of Judge Thornburg’s CJRS retirement benefits by CJRS officials during his service as Attorney General of North Carolina from 1985 through 1992). The legislature is presumed to act with full knowledge of prior and existing law. Polaroid Corp. v. Offerman, 349 N.C. 290, 303, 507 S.E.2d 284, 294 (1998), cert. denied, 526 U.S. 1098, 143 L. Ed. 2d 671 (1999). When the legislature chooses not to amend a statutory provision that has been interpreted in a specific way, we assume it is satisfied with the administrative interpretation. Id. Nevertheless, it is ultimately the duty of courts to construe administrative statutes; courts cannot defer that responsibility to the agency charged with administering those statutes. State ex rel. Util. Comm’n v. Public Staff, 309 N.C. 195, 306 S.E.2d 435 (1983).
This does not mean, however, that courts, in construing those statutes, cannot accord great weight to the administrative interpreta*320tion, especially when, as here, the agency’s position has been longstanding and has been met with legislative acquiescence. Polaroid Corp., 349 N.C. at 303, 507 S.E.2d at 294 (citing State v. Emery, 224 N.C. 581, 587, 31 S.E.2d 858, 862 (1944)); see Frye Reg’l Med. Ctr., Inc. v. Hunt, 350 N.C. 39, 45, 510 S.E.2d 159, 163 (1999) (holding that the interpretation of a statute given by the agency charged with carrying it out is entitled to great weight). Moreover, according great weight to the administrative interpretation in the face of legislative acquiescence is all the more warranted when, as in the instant case, the subject is a complex legislative scheme necessarily requiring expertise. See Thomas Jefferson Univ. v. Shalala, 512 U.S. 504, 512, 129 L. Ed. 2d 405, 415 (1994).3
In upholding the Board’s long-standing administrative interpretation, we express no opinion concerning the wisdom of the statutory prohibition on “double-dipping”—as this public policy determination was properly resolved by the General Assembly. See In re Appeal of Philip Morris U.S.A., 335 N.C. 227, 231, 436 S.E.2d 828, 831 (1993) (whether to prohibit or allow contingent fee arrangements for private tax auditors is a public policy determination for the General Assembly), cert. denied, 512 U.S. 1228, 129 L. Ed. 2d 2726 (1994); State v. Ballance, 229 N.C. 764, 767, 51 S.E.2d 731, 733 (1949) (“[A] court is not concerned with what the law ought to be, but its function is to declare what the law is.”). In any event, if the legislature chooses to permit “double-dipping” by those individuals who receive judicial retirement benefits and who return to active service as state employees, it may do so. See Martin v. N.C. Housing Corp., 277 N.C. 29, 41, 175 S.E.2d 665, 671-72 (1970) (holding that the General Assembly is to establish the public policy of this state). Indeed, it is clear from the ratification and subsequent repeal of N.C.G.S. § 135-72 that the legislature knows how to modify the administrative interpretation of a retirement statute when it wishes to do so.
For the reasons stated, the Court of Appeals properly affirmed the trial court’s decision to affirm the Board’s suspension of plaintiff’s CJRS benefits during his service as Chair of the North Carolina Utilities Commission from 1 August 1994 through 31 December 1996.
*321AFFIRMED.
. The name of the Judicial Retirement System was changed in 1985 from the “Uniform Judicial Retirement System” to the “Consolidated Judicial Retirement System.” Except where otherwise noted, our references to the “CJRS” apply generally to the Judicial Retirement System and not to the system in place at any particular time.
. We apply the version of our General Statutes in effect when plaintiff’s retirement benefits vested in August 1984. See Faulkenbury v. Teachers' & State Employees' Ret. Sys. of N.C., 345 N.C. 683, 690, 483 S.E.2d 422, 427 (1997); Simpson v. N.C. Local Gov't Employees' Ret. Sys., 88 N.C.. App. 218, 224, 363 S.E.2d 90, 94 (1987), aff’d per curiam, 323 N.C. 362, 372 S.E.2d 559 (1988).
. We recognize that, when the language of the statute is clear and unambiguous, the court must give effect to its meaning because the plain language evincing the intent of the legislature cannot be evaded by an administrative body or a court under the guise of construction. See Davis v. N.C. Dep’t of Human Res., 349 N.C. 208, 212, 505 S.E.2d 77, 79 (1998); Watson Indus. v. Shaw, 235 N.C. 203, 211, 69 S.E.2d 505, 511 (1952). The retirement statutes at issue, however, are neither clear nor unambiguous.