The appellant, Alice Harris, the widow of Jack Harris, challenges a reduction in her husband's workers' compensation benefits pursuant to RCW 51.32.225. RCW 51.32.225(1) provides for a reduction in workers' compensation benefits for those receiving Social Security retirement benefits. It contains an exception to the reduction where a worker was "receiving permanent total disability benefits prior to July 1, 1986." Harris urges this court to construe this exception as including not only workers actually receiving benefits prior to July 1, 1986, but also those who are subsequently determined to have sustained permanently disabling injuries prior to that date. She also argues the statute violates the equal protection clauses of the federal and state constitutions, as well as the vested rights clause, article 1, section 23 of the state constitution. In addition, amicus Washington State Trial Lawyers Association (hereafter WSTLA) contends that federal law preempts RCW 51.32.225.
We agree with the trial court's conclusion that Harris does not fall within the exception to the offset provision.1 We also affirm the trial court's conclusion that RCW 51.32-.225 violates neither the vested rights clause of our state constitution nor the equal protection clauses of the state and federal constitutions. In addition, we hold that federal law does not preempt the offset contained in RCW 51.32-
The appellant's husband, Jack Harris, filed an industrial insurance claim in June 1979 for work-related injuries caused *465by exposure to asbestos. The Department of Labor and Industries (hereafter the Department) accepted his claim and began paying Harris temporary total disability payments, also known as time-loss orders. Until recently, he received those payments.2 Harris was examined numerous times from 1979 to 1986. The doctor who examined him repeatedly stated that his condition was permanent and that he did not expect that Harris would be able to return to work. Although Harris might have initiated an inquiry under RCW 51.32.055(2) to determine whether he was entitled to receive permanent total disability benefits, he did not do so.
RCW 51.32.225(1), which became effective July 1, 1986, provides:
For persons receiving compensation for temporary or permanent total disability under this title, the compensation shall be reduced by the department to allow an offset for social security retirement benefits payable under the federal social security, old age survivors, and disability insurance act, 42 U.S.C. This reduction shall not apply to any worker who is receiving permanent total disability benefits prior to July 1, 1986.
Dining legislative debate, two major justifications for the offset emerged: avoiding duplicative benefits and limiting the cost of industrial insurance. House floor remarks by Representatives Chandler and King on second reading of SHB 1875, 49th Legislature (Feb. 12, 1986).
At the time RCW 51.32.225 became effective, Harris was 75 years old. He was collecting both Federal Social Security retirement benefits and state temporary total disability payments. On August 11,1986, the Department issued an order reducing Harris's compensation payments by the amount of Social Security retirement benefits he was receiving.
Harris appealed the Department's order to the Board of Industrial Insurance Appeals (hereafter the Board). The Board considered only the statutory construction of RCW 51.32.225. The parties reserved the right to raise questions of fact or other legal and jurisdictional questions in further *466proceedings. The industrial appeals judge affirmed the Department's decision to reduce Harris's temporary total disability benefits by the amount of Social Security retirement benefits Harris was receiving. He found that the exception to the offset provision contained in RCW 51.32.225(1) only applied to those who were actually receiving permanent total disability benefits as of July 1, 1986. Harris sought review by the full Board. On March 1, 1989, the Board affirmed that interpretation of RCW 51.32.225 by a 2-to-l vote.
Harris appealed the Board's decision to the Superior Court for Mason County. The Department and Harris filed cross motions for summary judgment. Harris argued that the exception to the offset contained in RCW 51.32.225(1) should be construed as including not only those receiving permanent total disability payments as of July 1, 1986, but also those injured prior to that date who would subsequently be deemed eligible for such payments. Harris also argued that RCW 51.32.225 unconstitutionally abrogated vested rights and violated equal protection guaranties of both the federal and state constitutions. No preemption argument was made to the trial court. Harris also countered the Department's contention that reconsideration of unappealed time-loss orders are barred by res judicata.
On November 16, 1990, the Superior Court granted the Department's summary judgment motion. It rejected the constitutional challenges, and affirmed the Board's interpretation of the statute. It also found that unappealed department orders determining disability benefit levels are final and reconsideration of them is barred by res judicata. Harris sought direct review in this court. We accepted review, and now affirm the trial court.
II
Both federal and state governments have attempted to coordinate benefits paid to workers. In 1965, the federal government, fearing that duplicative state and federal benefits would erode state and federal programs and discourage *467workers from returning to work, passed legislation to coordinate benefits. For those under 65, federal law provides that the total of Federal Social Security disability and old-age benefits, when added to state or local workers' compensation, will be reduced if they exceed the higher of (1) 80 percent of the worker's former salary or (2) the total of federal disability and old-age insurance benefits. 42 U.S.C. § 424a(a). The United States Supreme Court rejected a challenge to this federal offset program on due process and equal protection grounds in Richardson v. Belcher, 404 U.S. 78, 30 L. Ed. 2d 231, 92 S. Ct. 254 (1971).
Several states, including Washington, have passed what are sometimes called "reverse offset provisions" which effectively shift costs back to the federal government by reducing state workers' compensation benefits to account for Federal Social Security benefits. 2 Social Security Law and Practice § 26:66 (1987). This court has upheld the validity of RCW 51.32.220, enacted originally in 1975, which reduced state workers' compensation benefits for those under 65 who were receiving federal old-age, survivors or disability benefits. Ravsten v. Department of Labor & Indus., 108 Wn.2d 143, 148-49, 736 P.2d 265 (1987). In 1986 the Legislature added RCW 51.32.225, the statute at issue in this case. It allows workers' compensation benefits to be reduced by the amount of Federal Social Security retirement benefits a worker receives. In effect, RCW 51.32.225 extended Washington's reverse offset to cover those 65 and older who receive federal retirement benefits.
Ill
We first address the federal preemption argument because it raises the issue of whether the Legislature had the authority to enact RCW 51.32.225.
A
Amicus WSTLA raises for the first time the argument that RCW 51.32.225 violates the supremacy clause of the federal constitution. This court generally does not consider issues that are raised only by an amicus. State v. Gonzalez, *468110 Wn.2d 738, 752 n.2, 757 P.2d 925 (1988); Coburn v. Seda, 101 Wn.2d 270, 279, 677 P.2d 173 (1984); see also RAP 12.1(a). We do, however, have inherent authority to consider issues not raised by the parties if necessary to reach a proper decision. Alverado v. WPPSS, 111 Wn.2d 424, 429-30, 759 P.2d 427 (1988), cert. denied, 490 U.S. 1004 (1989); see also RAP 12.1(b). This court in Alverado decided to consider a federal preemption issue not raised by the parties, noting that there is no dispute about the legal contours of federal preemption doctrine. Alverado, at 429-30.
Unlike the Alverado case, however, the preemption issue was not raised at the trial court. Generally, this court does not consider an issue that was not raised at the trial court. New Meadows Holding Co. v. Washington Water Power Co., 102 Wn.2d 495, 498, 687 P.2d 212 (1984); see also RAP 2.5(a). This court does, however, have discretion to consider issues not raised at the trial court. Obert v. Environmental Research & Dev. Corp., 112 Wn.2d 323, 333, 771 P.2d 340 (1989). It is appropriate to consider the preemption issue in this case inasmuch as numerous similar cases are currently pending that challenge the validity of RCW 51.32.225.
B
Amicus WSTLA argues that federal law expressly or implicitly preempts the offset provision of RCW 51.32.225. We start with the "basic assumption that Congress did not intend to displace state law." Maryland v. Louisiana, 451 U.S. 725, 746, 68 L. Ed. 2d 576, 101 S. Ct. 2114 (1981). Whether federal law preempts state action is largely a matter of statutory construction. L. Tribe, American Constitutional Law § 6-26, at 480 (2d ed. 1988).
The core of amicus's argument is that 42 U.S.C. § 424a(d) is evidence of congressional intent to preempt state reverse offsets of federal retirement benefits. In order for this court to find preemption under this theory, we must find that "the federal statute clearly evinces a congressional intent to preempt state law". (Italics ours.) State v. Williams, *46994 Wn.2d 531, 538, 617 P.2d 1012, 24 A.L.R.4th 1191 (1980). 42 U.S.C. § 424a(d) provides:
The reduction of benefits required by this section shall not be made if the law or plan described in subsection (a)(2) of this section under which a periodic benefit is payable provides for the reduction thereof when anyone is entitled to benefits under this subchapter on the basis of the wages and self-employment income of an individual entitled to benefits under section 423 of this title, and such law or plan so provided on February 18, 1981.
42 U.S.C. § 424a(d). This provision allows states to create a reverse offset for federal disability benefits payable under 42 U.S.C. § 423. The federal government will not impose its own reduction if the state had its reverse offset program in operation as of February 18, 1981. The purpose of 42 U.S.C. § 424a(d) is to avoid a double offset. Sciarotta v. Bowen, 837 F.2d 135, 140 (3d Cir. 1988) (quoting Swain v. Schweiker, 676 F.2d 543 (11th Cir.), cert. denied, 459 U.S. 991, 74 L. Ed. 2d 388, 103 S. Ct. 349 (1982)). The effect of this provision is that it allows the state to shift costs to the federal government through its reverse offset program.
Amicus argues that 42 U.S.C. § 424a(d) only allows states to enact reverse offsets for federal disability payments. Because 42 U.S.C. § 424a(d) makes no mention of reverse offsets for federal retirement benefits, amicus concludes that Congress intended to prohibit them.
Unlike other benefits cases where preemption has been found, congressional intent to preempt state law is lacking here. For example, in Rose v. Arkansas State Police, 479 U.S. 1, 93 L. Ed. 2d 183, 107 S. Ct. 334 (1986) the Court held that Arkansas's attempts to reduce state death benefits under its workers' compensation act by the amount received under the Public Safety Officers Death Benefits Act were preempted. The federal statute explicitly provided that the benefit was to be in addition to any other benefits. 42 U.S.C. § 3796(e). In Raskin v. Moran, 684 F.2d 472 (7th Cir. 1982), the court held that a Wisconsin statute which reduced state "reserve" judges' salaries by an amount equal *470to any Social Security retirement benefits conflicted with federal policy expressed in 42 U.S.C. § 403(f)(3), which prohibits reduction in Social Security benefits of persons over age 70 who continue to earn income. By contrast, 42 U.S.C. § 424a does not contain clear evidence of congressional intent to preempt state reverse offsets of Federal Social Security retirement benefits. We decline to infer preemption from Congress's silence.3
In addition, RCW 51.32.225 extended state reverse offsets to include those 65 and older who receive Federal Social Security retirement benefits. The federal offset provisions contained in 42 U.S.C. § 424a only apply a federal offset to those under 65. Accordingly, Congress has expressed no policy on state reverse offsets for federal disability or retirement benefits for those over 65.4
In Alverado, 111 Wn.2d at 431, we noted several other ways in which federal law can preempt state law. First, if Congress indicates an intent to occupy a given field, any state law falling within that field is preempted. Second, state law will also be preempted if it actually conflicts with federal law. Finally, we said that state law is preempted *471when it would hinder accomplishment of the purposes and objectives of federal law. Alverado, 111 Wn.2d at 431.
Amicus focuses solely on 42 U.S.C. § 424a to support its preemption argument. That statute does not express an intent to occupy the field of coordinating benefits. In fact, 42 U.S.C. § 424a(d) provides for some types of state reverse offsets, thus indicating a congressional interest in sharing the field of benefit coordination. Amicus also has not pointed to a conflict between the federal and state statutes. An actual conflict occurs where state and federal statutes are contradictory on their face and compliance with both is impossible. Florida Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 132, 142-43, 929, 10 L. Ed. 2d 248, 83 S. Ct. 1210 (1963).5
Finally, amicus has not shown that RCW 51.32.225 is at odds with the purposes and objectives of federal law. After all, the statute amicus relies on, 42 U.S.C. § 424a, is clear evidence of Congress's interest in coordinating benefits to avoid duplication.6 As indicated below in section VI(B), RCW 51.32.225 also avoids duplicative benefits. Therefore, RCW 51.32.225 is consistent with federal policy.
Congress has not made its intent to preempt state law in this area clear. Therefore, we hold that federal law does not preempt RCW 51.32.225.
IV
After setting forth reductions in temporary and permanent disability compensation for those who receive Social *472Security retirement benefits, RCW 51.32.225(1) provides an exception for those "receiving permanent total disability benefits prior to July 1, 1986." Even though permanent total disability payments were not actually received as of July 1, 1986, Harris claims that she should fall within the statutory exception to the offset. Her claim is based on the fact that her husband's allegedly permanent and disabling injuries were sustained prior to July 1, 1986.
This court's primary duty in interpreting statutes is to give effect to the Legislature's intent. WPPSS v. General Elec. Co., 113 Wn.2d 288, 778 P.2d 1047 (1989). On its face, the statutory exception appears unambiguous. It simply makes an exception for those who are receiving permanent disability benefits as of a certain date. To receive is to "take possession or delivery of" something. Webster's Third New International Dictionary 1894 (1976). Jack Harris was not taking possession or delivery of permanent disability benefits on July 1, 1986. He was only receiving temporary total disability payments on that date. He had not even requested a determination as to whether he was permanently disabled under RCW 51.32.055(2). Essentially, the petitioner would have us read the term "receive" to mean "subsequently determined eligible to receive". This would improperly stretch the language of the statute.7
In addition, as the Board of Industrial Insurance Appeals indicated, if the Legislature had wanted to broaden the class of individuals that were not subject to the Social Security offset to include those who were injured prior to July 1, 1986, but not found to be permanently and totally disabled until after that date, it could have used language similar to *473that in RCW 51.32.220(7). In re Social Security Retirement Offset Cases (Board of Industrial Insurance Appeals), at 7. The 1982 amendments to RCW 51.32.220(1) raised the age limit for the disability offset from age 62 to age 65. The Legislature also provided that the change in the law "shall apply with respect to workers whose effective entitlement to total disability compensation begins after January 1, 1983." (Italics ours.) RCW 51.32.220(7). As a result, even when a person was placed on the pension rolls after January 1,1983, but that person's effective date of total disability was prior to January 1, 1983, he or she would still be exempt from the expanded disability offset. Therefore, had the Legislature intended to include those who are determined to be eligible to receive benefits subsequent to July 1, 1986, it could have used language similar to that in RCW 51.32.220(7).
We are not persuaded by Harris's three counterarguments. First, she argues that in Ashenbrenner v. Department of Labor & Indus., 62 Wn.2d 22, 380 P.2d 730 (1963), this court held that workers' rights to compensation vest at the time of their injuries. She also argues that the language of industrial insurance legislation is to be construed liberally in favor of a claimant. Finally, Harris argues that this court should defer to the Department's interpretation of the statute, which coincides with her own interpretation. Given the fact that the statute is not ambiguous, these arguments are not persuasive.
The court in Ashenbrenner held only that it would presume the law in effect on the date of an injury controls the rights of a worker absent clear legislative intent to the contrary. That opinion suggests the Legislature can change this rule retrospectively if it clearly expresses an intent to do so. Ashenbrenner, 62 Wn.2d at 26-27; see also Bodine v. Department of Labor & Indus., 29 Wn.2d 879, 889, 190 P.2d 89 (1948) (statutes construed prospectively "unless an intent to the contrary has been manifested by the most clear and unequivocal expression"). Unlike the amendments at issue in Ashenbrenner, the terms "receiving permanent total disability benefits" in RCW 51.32.225 unambiguously indicate *474the Legislature did not intend that the date of injury should govern whether an exception to the offset applies. Therefore, Harris's reliance on Ashenbrenner is misplaced.
Next, Harris argues that where an ambiguity exists in industrial insurance legislation, the language is to be construed liberally in favor of the claimant, citing Sacred Heart Med. Ctr. v. Carrado, 92 Wn.2d 631, 635, 600 P.2d 1015 (1979). Because we find RCW 51.32.225 unambiguous, we cannot construe the statute, and we must simply apply it. Tacoma Telco Fed. Credit Union v. Edwards, 94 Wn.2d 666, 669, 619 P.2d 363 (1980); see also Lowry v. Department of Labor & Indus., 21 Wn.2d 538, 542, 151 P.2d 822 (1944) (acknowledging liberal construction in favor of beneficiaries under the workers' compensation act, but refusing to construe a statute that is unambiguous).
Finally, Harris argues that the Department's own policy was that the Social Security retirement offset will not be applied where it determines that an individual is permanently disabled after June 30, 1986. An administrative agency's interpretation of a statute, however, is not relevant in determining legislative intent where a statute is unambiguous. Lee v. Jacobs, 81 Wn.2d 937, 940, 506 P.2d 308 (1973).
In this case the Department neither considered nor determined whether Harris was totally and permanently disabled prior to July 1, 1986. Therefore, we hold that Harris does not fall within the exception to the offset provision contained in RCW 51.32.225(1).8
V
Harris next argues that RCW 51.32.225 abrogates vested contractual rights in violation of Const, art. 1, § 23, which provides that "[n]o bill of attainder, ex post facto law, or law *475impairing the obligations of contracts shall ever be passed." In a nutshell, the issue is whether a worker has a vested contractual right to a certain level of workers' compensation at the time of an injury.
We have stated the general rule regarding what rights are vested:
A vested right, entitled to protection from legislation, must be something more than a mere expectation based upon an anticipated continuance of the existing law; it must have become a title, legal or equitable, to the present or future enjoyment of property, a demand, or a legal exemption from a demand by another.
Godfrey v. State, 84 Wn.2d 959, 963, 530 P.2d 630 (1975). The exception to the offset for those receiving permanent total disability benefits prior to July 1, 1986, eliminates any infringement upon vested rights. After all, workers actually receiving permanent total disability benefits prior to July 1, 1986, do not have their benefits offset. As of that date, Harris had not even initiated an inquiry into whether he was permanently and totally disabled. Where the Department has neither considered nor determined whether a worker is permanently and totally disabled, that worker has a future expectation of benefits, not a vested right.9
But Harris counters that workers' rights to a level of compensation vest at the time of injury, relying on Ashenbrenner v. Department of Labor & Indus., 62 Wn.2d 22, 380 P.2d 730 (1963). As we have noted already, Ashenbrenner only required that the Legislature make its intent clear that its legislation was meant to operate retrospectively. It does not stand for the proposition that an individual's right to workers' compensation benefits vests at the time of an injury. In a different context, this court has stated that with *476regard to industrial insurance rights, "the Legislature is perfectly able to designate an effective date other than a date of the injury when it chooses to do so." Seattle Sch. Dist. 1 v. Department of Labor & Indus., 116 Wn.2d 352, 361, 804 P.2d 621 (1991). Therefore, we find that a worker's right to compensation does not vest at the time of injury.
In addition, the constitutionality of other states' offset provisions has been consistently upheld as against impairment of contract attacks. 4 A. Larson, Workmen s Compensation § 97.35(b) (1990) (citing American Bankers Ins. Co. v. Little, 393 So. 2d 1063 (Fla. 1980)); Baker v. List & Clark Constr. Co., 222 Kan. 127, 563 P.2d 431 (1977). While Harris does cite some cases from other states suggesting that workers' rights vest at the time of injury, none of them involved a constitutional challenge to state reverse offsets.
Therefore, we hold that RCW 51.32.225(1) does not abrogate a worker's vested rights where the Department neither considered nor determined whether that worker was permanently and totally disabled prior to the passage of that legislation.
VI
Harris also argues that the offset provision of RCW 51.32-.225 violates equal protection under both the federal and state constitutions. U.S. Const. amend. 14, § 1; Const, art. 1, § 12.10 The main thrust of Harris's equal protection argument is that the offset provision applies only to Social Security retirement benefits, but not to other benefits or support income. In addition, Harris argues that reducing state disability benefits to account for federal retirement benefits does not further a legitimate governmental purpose.
A
The first step in equal protection analysis is determining the standard of review. State v. Smith, 93 Wn.2d 329, 610 *477P.2d 869, cert. denied, 449 U.S. 873 (1980). Harris argues that intermediate or strict scrutiny ought to apply to the legislative classifications created by RCW 51.32.225. The case which she relies most heavily on, Macias v. Department of Labor & Indus., 100 Wn.2d 263, 668 P.2d 1278 (1983), is easily distinguishable from this case. In Macias workers alleged that a statute which required seasonal workers to earn $150 from each employer to be eligible for workers' compensation violated equal protection. In analyzing the workers' equal protection claims, this court applied strict scrutiny because it penalized, in effect, a worker's fundamental right to travel. Macias, 100 Wn.2d at 273. Harris, however, has not shown that any fundamental right is affected by the Social Security offset provision of RCW 51.32-.225. Heightened scrutiny is also appropriate where a "suspect" classification is involved. Darrin v. Gould, 85 Wn.2d 859, 865-66, 540 P.2d 882 (1975). Harris has not alleged that RCW 51.32.225 creates a suspect classification based on race, alienage, or national origin.
Because RCW 51.32.225 is economic legislation which neither sets up a suspect class nor affects a fundamental right, rational basis review is appropriate. Richardson v. Belcher, 404 U.S. 78, 81, 30 L. Ed. 2d 231, 92 S. Ct. 254 (1971); Conklin v. Shinpoch, 107 Wn.2d 410, 416-17, 730 P.2d 643 (1986); Standing v. Department of Labor & Indus., 92 Wn.2d 463, 467, 598 P.2d 725 (1979); Sanchez v. Department of Labor & Indus., 39 Wn. App. 80, 88, 692 P.2d 192 (1984), review denied, 103 Wn.2d 1039 (1985).
B
We ask three questions in analyzing equal protection claims under the rational basis test:
1. Does the classification apply alike to all members within the designated class?
2. Do reasonable grounds exist to support a distinction between those within and without each class? and
3. Does the class have a "rational relationship" to the purpose of the legislation?
*478Skagit Motel v. Department of Labor & Indus., 107 Wn.2d 856, 860, 734 P.2d 478 (1987). Only the second and third questions of the Skagit Motel analysis are raised in this case.11
Harris raises the second question by arguing that the offset provision in RCW 51.32.225 violates equal protection by applying only to Social Security retirement benefits, but not to benefits or support income received from another source. Similar setoffs, however, have withstood equal protection attacks. For example, in Richardson v. Belcher, 404 U.S. 78, 30 L. Ed. 2d 231, 92 S. Ct. 254 (1971), the Court held that the federal government's offset provision did not violate equal protection. In Richardson the Court declined to consider a similar argument:
We have no occasion, within our limited function under the Constitution, to consider whether the legitimate purposes of Congress might have been better served by applying the same offset to recipients of private insurance ....
404 U.S. at 84. We approved the reasoning of Richardson in Ravsten v. Department of Labor & Indus., 108 Wn.2d 143, 736 P.2d 265 (1987). See also Boehm v. Industrial Comm'n, 738 P.2d 804, 806-07 (Colo. Ct. App. 1987).
The Court's reasoning in Richardson is similar to a principle this court recognizes in equal protection cases: that the Legislature may address a problem in a piecemeal fashion without violating an individual's rights under equal protection. Crown Zellerbach Corp. v. Department of Labor & Indus., 98 Wn.2d 102, 653 P.2d 626 (1982). Therefore, the offset provision does not violate equal protection because it *479applies only to Social Security retirement benefits, and not to private pensions or other sources of benefits.
Harris, however, attempts to distinguish Ravsten and Richardson by arguing that those cases involved state and federal efforts to offset disability benefits. In both cases, governmental efforts to avoid duplication of disability benefits were deemed legitimate legislative purposes. The legislative history of RCW 51.32.225 suggests that avoiding duplication in benefits or "double dipping" was a major factor behind the statute. House floor remarks by Representatives Chandler and King, on second reading of SHB 1875, 49th Legislature (Feb. 12, 1986). Harris argues that RCW 51.32.225, unlike the statutes considered in Ravsten and Richardson, reduces state disability payments to account for federal retirement benefits. Harris argues that the purposes of disability and retirement benefits are distinct. Thus, Harris concludes RCW 51.32.225 does not serve a legitimate purpose because it does not avoid duplication benefits. Essentially, this raises the third question of the Skagit Motel equal protection analysis: Does the classification have a rational relation to the purpose of the statute?
Other state courts have considered the legitimacy of "duplication of benefits" rationales for offsets or reductions of benefits in similar contexts, and have reached different results. For example, the Supreme Court of Florida in Sasso v. Ram Property Mgt., 452 So. 2d 932 (Fla.), appeal dismissed, 469 U.S. 1030 (1984) considered the validity of a Florida statute which provided that wage-loss benefits terminated when an injured employee reached age 65. The court affirmed the trial court's conclusion that the exclusion of those over 65 was not rationally related to the prevention of "double dipping" because Social Security retirement benefits do not serve the same purpose as wage-loss benefits. Sasso, 452 So. 2d at 934 n.3. The court in Sasso, however, found that there were other legitimate purposes for termination of benefits, such as reducing fiinge benefits to reflect a productivity decline with *480age, inducing older workers to retire, and reducing the cost of workers' compensation premiums. 452 So. 2d at 934 n.3.
On the other hand, in Brown v. Goodyear Tire & Rubber Co., 3 Kan. App. 2d 648, 599 P.2d 1031 (1979), aff'd, 227 Kan. 645, 608 P.2d 1356, appeal dismissed, 449 U.S. 914 (1980), the court found that termination of state disability benefits from the date a claimant becomes entitled to old-age Social Security benefits did not create an arbitrary classification lacking rational justification. The court in Brown characterized the disability benefits as a form of wage-loss protection, and found termination of those benefits to be a rational way of avoiding duplicative benefits. See also Baker v. List & Clark Constr. Co., 222 Kan. 127, 130-32, 563 P.2d 431, 434-35 (1977) (holding that reduction in workers' compensation benefits due to dependents of deceased employee if dependents are also receiving Social Security benefits did not violate equal protection). The Brown and Baker decisions are consistent with the view of a leading treatise on workers' compensation:
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. . . .
(Footnote omitted.) 4 A. Larson, Workmens Compensation § 97.10 (1990). We find Larson's analysis persuasive. State disability benefits and federal old-age Social Security benefits serve the same purpose: to restore earnings due to wage loss. The cause of wage loss — whether it be old age, disability, or unemployment — is irrelevant. RCW 51.32.225 serves a legitimate purpose in avoiding duplication of benefits. In addition, during discussion of the bill in the State Legislature other legitimate reasons for the offset were mentioned. Saving money for the state fund and reducing industrial *481insurance premiums were also on the minds of legislators. House floor remarks by Representatives Chandler and King, 12 supra.
There were several legitimate reasons for the Legislature to enact RCW 51.32.225. RCW 51.32.225 does not violate the equal protection clauses of the state and federal constitutions.
VII
Harris argues that the trial court should not have determined the res judicata effect of unappealed temporary total disability payments, also known as time-loss orders, which Harris received. The Department has not responded to this argument. Harris argues that the parties entered a stipulation to the effect that this issue would be reserved until litigation on the other issues was resolved. The stipulation does suggest that the parties intended to reserve this issue. Nevertheless, Harris argued this issue on summary judgment at the trial court level. It does not appear from the record that petitioner objected to the trial court considering this issue. Generally, issues not raised at the trial court cannot be raised on appeal. New Meadows Holding Co. v. Washington Water Power Co., 102 Wn.2d 495, 498, 687 P.2d 212 (1984); see also RAP 2.5(a). Because Harris did not object to consideration of the effect of unappealed time-loss orders at the trial court, we decline to consider this argument.
*482We affirm the trial court's decision granting summary judgment for the Department.
Dore, C. J., and Brachtenbach, Dolliver, Andersen, Durham, and Smith, JJ., concur.
Harris suggests that there is an ambiguity in the trial court's interpretation of the exception to the offset provision in RCW 51.32.225(1). When read in context, the trial court agreed with the Board of Industrial Insurance Appeals' interpretation of that exception: only those receiving permanent total disability benefits before July 1, 1986, are exempt from the offset.
The day before oral argument Jack Harris's attorney informed the court that he is now dead. Alice Harris was substituted as plaintiff/appellant.
The dissent cites Kreidler v. Eikenberry, 111 Wn.2d 828, 835, 766 P.2d 438 (1989) and State v. Williams, 94 Wn.2d 531, 537, 617 P.2d 1012 (1980) to support its argument that Congress, by its failure to mention state offsets for retirement benefits, intended to prohibit them. The relevant portions of both these cases only dealt with a principle of statutory construction, namely that "expressio unius est exclusio alterius" (express mention of one thing implies exclusion of another). The rules we apply in considering federal preemption issues are different, because we normally require clear expression of congressional intent before we will find preemption.
Amicus correctly notes that the federal largess of 42 U.S.C. § 424a(d) applies only to state reverse offset programs enacted prior to February 18, 1981. 2 Social Security Law and Practice § 26:65 (1987); 4 A. Larson, Workmen s Compensation § 97.35(a) (1990). The State's first offset provision, RCW 51.32.220, was enacted in 1975, before the cutoff date. Amicus insists, however, that RCW 51.32.225 runs afoul of the time limit because it was enacted in 1986. Amicus fails to note, however, that 42 U.S.C. § 424a applies only to offsets for those under 65. Therefore, this limitation has no effect on state efforts to offset federal benefits paid to those 65 and older. Furthermore, the time limit contained in 42 U.S.C. § 424a(d) only applies to state offsets of disability benefits, not state offsets of retirement benefits.
Recently, the United States Supreme Court has stated that the situation where a state law is at odds with the purposes and objectives of federal law should also be deemed a form of preemption through actual conflict. Wisconsin Pub. Intervenor v. Mortier,_U.S._, 115 L. Ed. 2d 532, 111 S. Ct. 2476, 2482 (1991).
The dissent argues the application of an offset to Harris's state disability benefits conflicts with the overall goal of the Social Security Act of "assuring that workers receive their retirement benefits." Dissent, at 488. The dissent does not mention the fact that the level of Harris's retirement benefits remains unaltered. Raskin v. Moran, 684 F.2d 472 (7th Cir. 1982) is distinguishable because there Congress expressly stated that there be no reduction in Social Security payments for income earned past the age of 70. Congress has not said the same thing about state disability payments.
The dissent argues this provision is ambiguous, without demonstrating how one could interpret the term "receiving" differently. It deviates from a fundamental principle of statutory construction: that we will not construe unambiguous language in a statute. King Cy. v. Taxpayers of King Cy., 104 Wn.2d 1, 700 P.2d 1143 (1985). Only if the statute is ambiguous would we be able to employ a liberal construction to it for the benefit of the injured worker. The Department and one member of the Board of Industrial Insurance Appeals made the same error as the dissent by construing language which is clear and unambiguous.
The dissent wrongly suggests that Harris is being penalized "based solely on factors beyond [his] control." Dissent, at 483. Jack Harris always had the option to seek a determination of whether his injury was permanent. RCW 51.32.055. He failed to do so. Even though RCW 51.32.055 does not "mandate” that those who are disabled seek a determination of permanent disability, it provides a mechanism whereby an injured worker may secure his or her rights to a level of compensation.
Admittedly, Jack Harris's condition remained essentially the same for 7 years, and yet he was still receiving temporary total disability benefits. It is arguable that after receiving "temporary" benefits for 7 years, a person has more than a mere expectation of future benefits. Such an argument, however, is unpersuasive because Harris could have requested a determination of permanent disability at any time during this period. RCW 51.32.055(2). He failed to do so.
Harris has neither pointed to Washington precedents that would suggest that the state constitution provides greater protection in this case, nor has he briefed the factors set forth in State v. Gunwall, 106 Wn.2d 54, 720 P.2d 808, 76 A.L.R.4th 517 (1986). We will therefore not address the state constitutional issue without such briefing. In re Mota, 114 Wn.2d 465, 472, 788 P.2d 538 (1990).
Briefing and argument was presented in this case under the 3-part rational basis test in Skagit Motel. We will accordingly apply the 3-part test in this case. We note, however, that this court has recently applied a 1-part rational basis test in a case decided under the federal equal protection clause, and that this 1-part test is more consistent with federal precedent. See Foley v. Department of Fisheries, 119 Wn.2d 783, 837 P.2d 14 (1992) (citing Burlington Northern R.R. v. Ford,_U.S._, 119 L. Ed. 2d 432, 112 S. Ct. 2184, 2186 (1992)); see also State v. Coria, 120 Wn.2d 156, 171-72, 839 P.2d 190 (1992)). We would, however, reach the same result in this case under either test.
We have recently cautioned that a legislator's comments from the floor of the Legislature are not necessarily indicative of legislative intent. See Wilmot v. Kaiser Aluminum & Chem. Corp., 118 Wn.2d 46, 63, 821 P.2d 18 (1991) (citing North Coast Air Servs., Ltd. v. Grumman Corp., 111 Wn.2d 315, 326-27, 759 P.2d 405 (1988)). We emphasize that we do not rest our conclusion that RCW 51.32.225 is constitutional solely on the floor remarks of legislators. Unlike Wilmot and North Coast Air Servs., we are not being called upon to use floor remarks to interpret a statute. Instead, we use them to determine whether there was any conceivable justification for the classification created by RCW 51.32.225. We have stated that where finite state resources are involved, a statutory discrimination "will not be set aside if any state of facts reasonably may be conceived to justify it.' ” Caughey v. Employment Sec. Dep't, 81 Wn.2d 597, 599, 503 P.2d 460, 56 A.L.R.3d 513 (1972) (quoting Dandridge v. Williams, 397 U.S. 471, 485, 25 L. Ed. 2d 491, 90 S. Ct. 1153 (1970)).