This is a consolidated appeal from a decision of the Industrial Commission which upheld two closely related orders of the Public Employees Retirement Board (PERS Board). The appellants, Frederick Deonier and William Keller, were formerly employed by the Boise City Fire Department —Deonier from 1947 through 1981, and Keller from 1975 through 1982. Both men were injured on the job and negotiated lump sum monetary settlements of their worker’s compensation claims. Prior to their involuntary retirements, Deonier had contributed $18,121.69 to the Firemen’s Retirement Fund, and Keller had contributed $9,688.12. (Neither amount includes interest accrued thereon.) Subsequently, Deonier and Keller sought disability retirement benefits. The PERS Board granted the disability retirement benefits, but ordered, pursuant to I.C. § 72-1414, that the disability retirement benefits must be offset by the amount of the lump sum worker’s compensation benefits which they had previously received.
Both firemen appealed the PERS Board’s decision to the Industrial Commission pursuant to I.C. § 72-1423. The appeals were consolidated by the Commission because of the similarity of the legal issues. The Commission entered a final decision on appeal on September 29, 1986, affirming the setoff, but reducing the amount thereof. The primary issues raised by this appeal involve the legal interpretation of I.C. § 72-1414 by the PERS Board and the Commission, and the constitutionality of I.C. § 72-1414. We hold that, irrespective of constitutional infirmities, the interpretation of § 72-1414 by.the Board and the Commission is erroneous. We then hold § 72-1414 unconstitutional as an impairment of the right to contract and as a violation of equal protection of the law.
The legislation instituting the Firemen’s Retirement Fund (FRF) was enacted in 1945. See, I.C. § 72-1401 et seq. As originally enacted, § 14 of the Act (I.C. § 72-1414) provided that the amount of payments payable under the FRF “shall be reduced by the amount to which said paid fireman is entitled under the said Workman’s Compensation Law.”1
*723I.C. § 72-1414 has been restructured since 1945, but continues to provide for a setoff for worker’s compensation benefits paid, albeit in different subsections of the statute.2
INTERPRETATION OF IDAHO CODE, TITLE 72
On its face, I.C. § 72-1414 operates to decrease the amount of disability retirement benefits received by employees by the amount of worker’s compensation benefits they are entitled to receive. It is difficult to reconcile the provisions of I.C. § 72-1414 with I.C. § 72-318, which provides in pertinent part:
Invalid agreements — penalty.—(1) No agreement by an employee to pay any portion of the premiums paid by his employer for workmen’s compensation, or to contribute to the cost or other security maintained for or carried for the purpose of securing the payment of workmen’s compensation, or to contribute to a benefit fund or department maintained by the employer, or any contract, rule, regulation or device whatever design to relieve the employer in whole or in part from any liability created by this law, shall be valid. ... (Emphasis added).
In Skill v. Shill, 100 Idaho 433, 599 P.2d 1004 (1979), we commented upon the nature of retirement benefits received pursuant to the Idaho Firemen’s Retirement Fund.
The State of Idaho Firemen’s Retirement Fund establishes a pension plan funded by contributions from each paid fireman deducted from the fireman’s wages or salary. Other revenues are also added to the fund. ... A firefighter’s interest in the pension fund attributable to fund income from sources other than employee contributions is not a gratuity but a form of deferred compensation accrued by reason of the individual’s service ... (Emphasis added).
100 Idaho at 436, 599 P.2d at 1007.
Under like circumstances, the court in Symington v. City of Albany, 5 Cal.3d 23, 95 Cal.Rptr. 206, 485 P.2d 270 (1971), held that a city could not reduce the pension of a disabled fireman by the amount of workmen’s compensation the fireman had received, where Ca. Labor Code § 3751 provided that “[n]o employer shall exact or receive from any employee any contribution, or make or take any deduction from earnings of any employee, either directly or indirectly, to cover ... any part of the cost of [worker’s] compensation____”
In Symington, the city contributed an amount equal to employees’ contributions to the fund. The court allowed an offset of one-half of the worker’s compensation benefits received from the pension proportional to the city’s contribution to the pension fund. The court noted that to hold otherwise would “deprive [the fireman] of the benefit of his many years of contributions to the pension system and compel him, in violation of Labor Code section 3751, to pay indirectly for his own workmen’s compensation benefits.” 95 Cal.Rptr. at 207, 485 P.2d at 271.
While the California court opted for a partial offset to avoid violating Ca. Labor Code § 3751, we are not bound to accept their rationale in its entirety. Shill establishes that retirement benefits under the FRF are deferred compensation or wages. Requiring a firefighter to contribute to the cost of his own worker’s compensation benefits solely from his own contribution to his retirement fund violates the mandate of *724I.C. § 72-318 and undercuts a firefighter’s right to rely upon the benefits earned over a lifetime of work. However, even allowing a partial offset for those funds contributed to the Fund by the city would also deprive firemen of their own delayed wages. During wage negotiations, increases in retirement contributions by the city are often sought in lieu of increases in regular wages. The firefighter earns both payments from the city and is entitled to both. Further, one of the purposes underlying the enactment of the FRF as codified in § 72-1401 is the encouragement of long service in fire fighting. The State’s reading of I.C. § 72-1414 actively retards that worthy goal by encouraging firefighters to serve less time and risk less injury in order to preserve the full value of their own delayed wages.3
Importantly, allowing no offset comports with the mandate of I.C. § 72-1420, that “provisions of this chapter shall be liberally construed, with the object of promotion of justice and the welfare of the person subject to its provisions” (emphasis added), by not unjustly depriving retired firemen of a pension they have already earned.
It should be noted that the commission relied heavily upon Larson’s Treatise on Workmen’s Compensation in upholding the total offset. In particular, the commission focused upon the following language:
Wage-loss legislation is designed to restore to the worker a portion, such as one-half to two-thirds, of wages lost due to the three major causes of wage-loss: physical disability, economic unemployment, and old age. The crucial operative fact is that of wage-loss; the cause of the wage-loss merely dictates the category of legislation applicable. Now if a workman undergoes a period of wage loss due to all three conditions, it does not follow that he should receive three sets of benefits simultaneously and thereby recover more than his actual wage. He is experiencing only one wage loss and, in any logical system, should receive only one wage-loss benefit. This conclusion is inevitable, once it is recognized that workmen’s compensation, unemployment compensation, non-oceupational sickness and disability insurance, and old age and survivors’ insurance are all parts of a system based upon a common principle. (Emphasis added).
4 Larson, The Law of Workmen’s Compensation, § 97.10 (1971).
We cannot support any use of the above language from Larson to support the total offsetting of worker’s compensation benefits received from retirement benefits to which one is entitled. The language highlighted in the above quotation indicates that, under no circumstances, should a retired employee recover “more than his actual wage.” However, the central theme found in our statutes and case law is that retirement benefits are “wages.” Further, plaintiffs in this case have argued that, under no circumstance, could any retired firefighter receive more than one hundred percent of his wage pursuant to Idaho’s Worker’s Compensation Laws and the retirement benefits of the FRF, irrespective of any offsetting.4 The State has not disputed this assertion.
Additionally, even if a worker’s deferred wages, when coupled with monies received as worker’s compensation, total more than one-hundred percent of previous wages, such should not cut into the employee’s *725right to his retirement benefits, since worker’s compensation awards are received for discrete independent injuries — not as wages.
Both Larson, in-the foregoing quote, and the Commission, in relying upon it, misper; ceive the true nature of the bulk of worker’s compensation benefits when they reason that a worker may not recover “two or three sets of WAGE-LOSS benefits.” When a worker receives a permanent partial disability payment for loss of his leg at the hip, he is not receiving wages — he is being paid for loss of the leg. If, for example, the computer operator who lost a leg is rated for impairment when his condition stabilizes and he immediately returns to work at full pay, he nevertheless receives the permanent partial disability payments (either periodically or in a lump sum), not to replace wages, but as compensation for loss of the leg. Thus, the Commission, in utilizing Larson’s multiple wage-loss recovery theory, fails to recognize the true nature of the compensation payments.
In attempting to construe Title 72 in a manner which gives the maximum effect possible to all of its code sections, we must reverse the Commission, holding that the reasonable interpretation of I.C. § 72-1414 does not allow for any offsetting of worker’s compensation benefits from monies earned as deferred wages. We next consider whether the application of any offsetting would be constitutional as applied to the firemen under Idaho’s FRF.
IMPAIRMENT OF CONTRACT
In 1980, the legislature merged the Firemen’s Retirement Fund into the Public Employment Retirement System (PERS). Thereafter, all firefighters employed after October 1, 1980, received retirement benefits through PERS, while firefighters who were employed prior to that time and were members of FRF remained so. At that time, I.C. § 59-1356 provided:
Benefits payable. — The combined rights and benefits of paid firemen who were employed prior to October 1, 1980, shall, not be less than the rights and benefits they would have received from the firemen’s retirement fund, had the fund not been integrated with the employee system.
At the time of the enactment of I.C. § 59-1356, the legislature was operating within a context where all prior known cases in which I.C. § 72-1414 and § 72-1429P (now repealed) could have been applied by the State Insurance Fund, were these where the Fund did not offset worker’s compensation benefits received from FRF benefits allowed. Indeed, the State can point to no cases where the offset provisions of I.C. § 72-1414 or § 72-1429P (now repealed) were ever applied. The legislature must be presumed to have acted with at least some knowledge of this continuous and unequivocal administrative treatment of I.C. § 72-1414.5 Had the legislature wished to emphasize the setoff provisions of I.C. § 72-1414 and § 72-1429P (now repealed), they easily could have done so in 1980 when it redrafted many of the FRF provisions. Instead, in 1980 the legislature repealed I.C. § 72-1429P.6
As we have already seen, I.C. § 72-1414, despite its apparently clear wording, does not require offsetting should one also wish to give vitality to, and effectuate the purposes of, the other provisions of Title 72. In short, the State Insurance Fund could have been compelled to reject applying the setoff (as it chose to do in all cases prior to 1980) by its reading of Title 72 in its entirety. At any rate, á clear pattern of administrative action by the State Insurance Fund *726was established. Prior to 1980, then, retired firemen could rely upon the fact that the State Insurance Fund would not interpret § 72-1414 as requiring a setoff in cases of lump sum settlement agreements. Further, as already stated, I.C. § 59-1356 enjoins the diminution of firefighter’s rights received from the Firemen’s Retirement Fund subsequent to the merger with the PERS. Additionally, rights under pension plans are vested:
This court has adopted the rule ‘the rights of the employees in pension plans such as Idaho’s Retirement Fund Act are vested, subject only to reasonable modification for the purpose of keeping the pension system flexible and maintaining its integrity.’
Lynn v. Kootenai County Fire Protective Dist. #1, 97 Idaho 623, 627, 550 P.2d 126, 130 (1976) (quoting from Hanson v. City of Idaho Falls, 92 Idaho 512, 514, 446 P.2d 634, 636 (1968)). The new administrative interpretation of I.C. § 72-1414 does, then, materially alter the vested rights of firefighters subject to the FRF.
While no case we have found directly addresses a situation where an administrative agency unilaterally alters its previously developed policy to lessen a public employee’s right to receive benefits, our holding in Nash v. Boise City Fire Department, 104 Idaho 803, 663 P.2d 1105 (1983), remains instructive. In Nash, we held that a 1978 legislative amendment, limiting to three percent the cost of living adjustment to firemen’s retirement pensions, could not be applied to a firefighter retiring after the effective date of the amendment who had earned benefits by virtue of service prior to that date, as his rights were vested and the fund was not insolvent. In so holding, we characterized retirement plans in “contract” terms, while noting that strict definitions of retirement plans as either “gratuities” or “contracts” were not meaningful. Ultimately, we cited to Engen v. James, 92 Idaho 690, 693, 448 P.2d 977, 980 (1969), wherein we held that the legislature could not take away vested retirement rights of a Coeur d’Alene policeman, stating that “[t]his follows from the compensatory nature of pension plans____” id. 104 Idaho at 806, 663 P.2d at 1108, quoting from Engen, supra. We then adopted the analysis in Betts v. Board of Administration of Public Employee’s Retirement System, 21 Cal.3d 859, 148 Cal.Rptr. 158, 582 P.2d 614 (1978), which determined that subsequent legislative modifications of retirement systems may be sustained where “reasonable,” and that “[t]o be sustained as reasonable, alterations of employees’ pension rights must bear some material relation to the theory of a pension system and its successful operation____” 104 Idaho at 807, 663 P.2d at 1109, quoting from Betts, 148 Cal.Rptr. at 161, 582 P.2d at 617. We then held that the three percent “cap” for cost of living adjustments to the pension plan was not reasonable, as the FRF was neither insolvent nor unable to meet its financial obligations either then or in the near future. Accordingly, the “cap” unreasonably impaired vested rights of public employees and could not be sustained. See also, State of Montana v. Fire Department Relief Association, etc., 138 Mont. 172, 355 P.2d 670 (1960), wherein the court held that the portion of a statute providing for payment of disability pensions by the fire department relief association to members, which stated that no member of the association shall be entitled to receive a disability pension while also receiving an allowance or award under Montana Workmen’s Compensation Act was an unconstitutional impairment of contract. See also, Sheffield v. Alaska Public Employees’ Association, 732 P.2d 1083 (Alaska 1987).
In the instant case, it is not a subsequent legislative modification which has impinged upon vested rights, but a new administrative interpretation of an extant statute which was subsequently merged into a different retirement system. In any event, the result for the retired person is the same. The nature of the retirement benefit as a contract — a method of deferred compensation — remains the same regardless of which state entity has interpreted I.C. § 72-1414.
Plaintiffs Deonier and Keller were entitled to rely upon the State Insurance *727Fund’s prior interpretation of § 72-1414 (i.e., not applying any offset pursuant thereto), and the administrative alteration of such interpretation materially altered their contractual expectations regarding their vested right to receive their retirement benefits through the FRF.
EQUAL PROTECTION
We have previously stated the various standards for equal protection review in other cases interpreting provisions of the FRF:
Like all statutorily created classifications, the classifications created by Title 72, Chapter 14, must satisfy the equal protection requirements of the Fourteenth Amendment. If a classification does not involve a fundamental right such as the right to vote or if a classification has not been drawn upon traditionally suspect lines such as race, the Supreme Court of the United States has held that the classification does not offend the Fourteenth Amendment if the classification bears a rational or reasonable relationship to the purposes for which the statute was enacted. (Citations omitted).
Lynn, supra, 97 Idaho at 625-26, 550 P.2d at 128-29.
While utilizing the “rational basis” standard in Lynn, we also recognized and utilized the intermediate “means-focus” standard in Jones v. State Board of Medicine, 97 Idaho 859, 867, 555 P.2d 399, 407 (1976):
This new intermediate standard of equal protection review has been described as “means-focus” because it tests whether the legislative means substantially furthers some specifically identifiable legislative. end.
Id. at 867, 555 P.2d at 407.
A classification “must be reasonable, not arbitrary, and must rest upon some ground of difference having a fair and substantial relation to the object of the legislation, so that all persons similarly circumstanced shall be treated alike.”
Id. quoting from Reed v. Reed, 404 U.S. 71, 75-76, 92 S.Ct. 251, 254, 30 L.Ed.2d 225 (1971).
Utilizing either the “rational basis” or the “means-focus” standards of review, I.C. § 72-1414 fails to pass constitutional muster. First, I.C. § 72-1414 sets forth an arbitrary classification, since it burdens only those firefighters who are members of the FRF and are subject to involuntarily retirement because of injuries resulting in the award of worker’s compensation benefits. I.C. § 72-1414 classifies both on the basis of involuntary retirement versus voluntary retirement, and membership in the FRF versus the PERS system. Further, the classification is arbitrary as between the firefighter injured early in his career, who ultimately receives 100% of both his worker’s compensation and retirement, and the firefighter injured shortly before retirement who suffers the reduction. Under either of the three instances, the classification is arbitrary and unrelated to furthering a specifically identifiable legislative end.
I.C. § 72-1401 lists the purposes of the FRF as follows:
Purpose of Act. — The retirement, with continuance of pay for themselves, provision for dependents, and pay during temporary disability, and the encouragement of long service in firefighting service, of paid firemen becoming aged or disabled in the service of the state or any of its cities or fire districts, is hereby declared to be a public purpose of joint concern to the state and each of its cities and fire districts in the protection and conservation of property and lives and essential to the maintenance of competent and efficient personnel in fire service____
I.C. § 72-1414 is certainly not tailored to further the ends of I.C. § 72-1401. Instead, when read in the manner sought by the State, it distinguishes between those who are forced into involuntary retirement due to disabling on-the-job injuries (and resultant worker’s compensation claims) and those who are fortunate enough to retire on a voluntary basis. I.C. § 72-1429Q provides that, for those firemen retiring voluntarily and not qualifying for benefits under any other provision of the chapter, such fireman “shall be entitled to receive at the *728time of said termination one hundred percent (100%) of whatever sums he has contributed to the retirement account____” Likewise, employees who receive retirement benefits through PERS can rely both upon receipt of social security benefits and upon I.C. § 59-1320(2), which at least limits offsetting.
As already mentioned, it is hard to imagine how I.C. § 72-1414 could possibly further the stated legislative purpose of encouraging long-term service as a firefighter when, with each day worked, a firefighter increases the risk that he or she will be forced to take an involuntary retirement due to an on-the-job injury and will not only by physically impaired, but will also suffer the loss of a portion of his or her own deferred salary to pay for his or her own worker’s compensation benefits. Further, the State has presented no cogent reason for distinguishing between treatment of voluntary and involuntary firefighting retirees, nor has it presented any valid reason for the difference in treatment as between members of FRF and PERS. In Lynn v. Kootenai County Fire Protective Diet. #1, supra, we struck down as violative of equal protection another portion of Title 72, chapter 1400 — namely, a 1973 amendment to I.C. § 72-1429F, which resulted in firefighters with less service receiving more benefits than firefighters who were incapacitated after twenty-one or more years of service. We noted that:
The primary purpose of the legislature in enacting these amendments was to increase the retirement, benefits for firemen who retired either voluntarily or non-voluntarily; however, as applied to Lynn, these amendments operated to diminish his benefits. The 1973 amendment to I.C. § 72-1429F (citation omitted) must be declared to be unconstitutional as this classification violates the Fourteenth Amendment to the Constitution of the United States.
Id. 97 Idaho at 626, 550 P.2d at 129.
As in Lynn, the classification found in I.C. § 72-1414 fails under either the “rational basis” test or the “means-focus” analysis. It furthers neither purpose enunciated in I.C. § 72-1401 and, if we assume for the sake of argument that its purpose could be to strengthen the financial position of the FRF, there should at least be some evidence of FRF insolvency; there is none.
Finally, we must address our opinion in Brock v. City of Boise, 95 Idaho 630, 516 P.2d 189 (1973). In Brock, we upheld the constitutionality of I.C. § 72-1429P (now repealed), which also operated to limit benefits under the Firemen’s Retirement Fund Act to the extent they exceed those to which the recipient is entitled under the Worker’s Compensation Law. The majority opinion in that case relied extensively upon the Larson Treatise, again apparently in the mistaken belief that I.C. § 72-1429P operated only to prevent a “double recovery” to retirees. The dissent by Chief Justice Donaldson persuasively argued that I.C. § 72-1429P did deny firefighters who entered into agreements whereby they received periodic worker’s compensation benefits their right to equal protection of the laws, as § 72-1429P did not also require an offset against retirement benefits for lump sum worker’s compensation payments previously received. We find the dissent persuasive and also note that the dissent implicitly recognizes that it was, at that time, the longstanding practice that lump sum worker’s compensation benefits were not offset from retirement benefits. (See, discussion of impairment of contract, supra.)
In view of our holding that the offset provisions of I.C. § 72-1414 are unconstitutional, we note that Title 72, chapter 14 of the Idaho Code does provide for severability pursuant to I.C. § 72-1426:
Separability. — If any clause, section or provision of this chapter be found to be unconstitutional, the remainder of this chapter shall remain in full force and effect, notwithstanding such invalidity.
The remainder of Title 72, chapter 14 is unaffected by our holding.
THE CROSS-APPEAL
The State asserts that since permanent partial disability benefits are “income benefits” within the meaning of the Idaho *729Worker's Compensation statutes, the retirement board should attribute the receipt of same to periods of actual wage loss for purposes of offsetting pursuant to I.C. § 72-1414. In view of our holding that the offset provisions of I.C. § 72-1414 are inoperative as violative of equal protection of the law and contractual rights, the issue on cross-appeal is moot.
Reversed and remanded for proceedings consistent herewith. Costs to appellants, no attorney fees awarded.
BISTLINE, J., concurs. SHEPARD, C.J., concurs in the result. DONALDSON, J., sat but did not participate due to his untimely death.. I.C. § 72-1414(B) provided: "Any paid fireman incapacitated by injury in the course of duty, or by illness attributable wholly or partially to service as a paid fireman, shall be retired so long as such disability shall continue in a degree which prevents efficient service, and during such disability shall be paid from the said fund a monthly sum of Sixty-five Dollars: provided, however, that if any such paid fireman is entitled to receive compensation under the Workmen’s Compensation Law of the State of Idaho as it now exists, or shall hereafter be amended, the amount payable under this Act shall be reduced by the amount to which said paid firemen is entitled under the Workmen’s Compensation Law.”
I.C. § 72-1414(C) provided: “In event a paid fireman is killed or sustains injury, from which death results, while in performance of his duty, and leaves surviving him a widow, his widow shall, during the time she remains his widow and does not remarry, be paid from the said fund the monthly sum of Sixty-five Dollars; in event the widow of a fireman so killed, or whose death so results, shall remarry and there shall be, at the time of such remarriage, his minor child or minor children of deceased under the age of eighteen years, the payments aforesaid shall be paid to the widow, notwithstanding such remarriage, but for the sole benefit of such minor child or children under and until reaching the age of eighteen years: provided, however, that any sums payable to any widow or minor child or children of any fireman under this Act shall be reduced by any sum to which such widow or minor child or children may be entitled under the provisions of the Workmen’s Compensation Law of the State of Idaho.”
. In 1975, I.C. § 72-1414(B) provided: "Any paid fireman incapacitated by injury in the course of duty, or by illness attributable wholly or partially to service as a paid fireman, shall be retired so long as such disability shall continue in a degree which prevents efficient service, and during such disability shall be paid from the said fund a monthly sum of Ninety-five Dollars ($95.00): provided, however, that if any such paid fireman is entitled to receive compensation under the Workmen’s Compensation Law of the State of Idaho as it now exists, or shall hereafter be amended, the amount payable under this Act shall be reduced by the amount to which said paid fireman is entitled under said Workmen's Compensation Law.”
I.C. § 72-1414(G) provided: "Any fireman, widow, child or children of a fireman entitled to compensation under the Workmen’s Compensation Law, shall draw benefits under this Act only to the extent that the benefits under this Act exceed those to which he shall be entitled under the Workmen’s Compensation Law of Idaho.”
. We wish to comment upon the Industrial Commission’s commentary following its rejection of Symington, noting that "by reducing the pension benefits by the amount of workmen’s compensation benefits, the cost to the pension fund is reduced which may, depending upon how it is implemented, reduce the size of the contributions the fund requires from firemen.” In addition to being an entirely speculative mode of analysis, the commission appears to be implicitly advocating a system where “less is more” — where a reduction in the size of contributions and a concommitant reduction in the size of the benefit fund is a worthy goal. Such commentary demonstrates a complete lack of understanding of both the purposes of retirement funds and the sources of the monies deposited therein, and undermines the legislature’s stated intent of providing retirement benefits to firefighters.
. Indeed, under the statutory scheme, no firefighter subject to the FRF can receive more than sixty-five percent of his last average monthly salary as retirement benefits.
. Indeed, the record contains evidence of a legal opinion advising the State Insurance Fund issued by a Boise attorney, identifying the three cases in which offset provisions were not applied to lump sum settlement agreements.
. I.C. § 72-1429(P) was substantially similar to I.C. § 72-1414 and read:
Workmen’s Compensation Credit. — Any fireman, widow, child or children of a fireman entitled to compensation under the Workman’s Compensation Law, shall draw benefits under this Act only to the extent that the benefits under this Act exceed those to which he shall be entitled under the Workmen’s Compensation Law of Idaho.