This is an appeal by an employer and its surety from an order of the Industrial Commission awarding the claimant disability benefits upon the basis of a permanent partial disability equal to 44% as compared to the whole man. We affirm.
The facts are not in dispute. The claimant-respondent Baldner became a journeyman ironworker in 1964, and worked continuously in that trade until August, 1977. At that time, while he was employed by Bennett’s, Inc., he suffered an injury to his lower back while he was unloading heavy materials. Although he thought the problem would subside, it persisted and a few days later, while he was working on a scaffold, he sustained additional injury to his lower back.
Baldner sought treatment from an orthopedic surgeon, who initially prescribed conservative treatment, but when the condition did not improve, a laminectomy and fusion at the L4-5 and L5-S1 levels of the lumbar spine were performed. By August 29,1979, Baldner’s condition had stabilized and he was released from medical care. As a result of the back injury and the surgery, Baldner’s physical abilities are limited and he cannot perform the work of an iron-worker.
The testimony indicated that prior to August, 1977, Baldner had a history of recurrent back problems. Dr. Johnson, the orthopedic surgeon diagnosed Baldner’s condition as degenerative nerve disease with nerve impingement and arthritic changes in the joints in the posterior part of the back. He testified that Baldner’s 1977 injury aggravated his pre-existing degenerative condition and that the accident combined with the preexisting condition precipitated the need for surgery. Dr. Johnson testified that Baldner’s permanent partial impairment rating was equivalent to 15% of the whole man.
At the time of the injury, Baldner was 33 years old, had completed part of his freshman year of college and had completed courses such as welding and blueprint reading which would help him in his trade. *460Prior to the 1977 injury, Baldner earned $24,421.20 per year from ironworking, and also held two part-time jobs, one as assistant business agent for the Ironworker’s Union, from which he earned $3,600 per year, and another teaching the ironworker apprentice program at Boise State University, earning $1,800 per year. Thus his pre-injury annual income totalled $29,821.20. Since both part-time positions required the employee to be an active ironworker, Baldner could perform neither of those part-time jobs after the 1977 injury.
Following the stabilization of his condition, Baldner obtained employment teaching welding at Boise State University, earning $15,988.63 per year. He also earns an additional $720 per year for teaching a night course in blueprint reading thus bringing his total post-injury annual income to $16,708.63. To maintain his employment, Baldner must take teacher education courses, full-time during the summer and part-time dining the school year. He intends to earn a bachelor’s degree in education and work toward a master’s degree.
Baldner and the surety, State Insurance Fund, were unable to agree upon permanent partial disability benefits, and Baldner petitioned the Industrial Commission for a hearing on that issue. Following hearing, the Commission found the permanent partial disability to be equivalent to 44% of the whole man by measuring that disability in terms of Baldner’s decrease in wage earning capacity. The Commission found that defendants-respondents did not establish that Baldner could earn more than he was earning in his teaching positions at BSU and held that Baldner’s wage earning capacity accurately reflected the decrease in his ability to engage in gainful employment resulting from the injury.
Defendants-appellants Bennett’s, and its surety, the State Insurance Fund, first assert that the Commission erred by failing to apportion Baldner’s disability between his pre-existing physical impairment and his 1977 injury in accordance with I.C. § 72-406. The record is clear that Baldner indeed suffered from pre-existing congenital degenerative disk disease and arthritic changes prior to the time of his injury in 1977. However, the record is totally void of any evidence probative of the percentage of Baldner’s disability, if any, that should be attributed to his pre-existing condition. Further, the record reveals that neither the Commission nor the Referee considered apportionment of the disability to be at issue in the proceedings below. As framed by the parties, the major issue before the Commission involved the extent of Baldner’s permanent partial disability. Baldner’s application also requested additional retraining benefits and reasonable attorney’s fees, but both of those issues were specifically resolved against Baldner and are not presented here on appeal. The answer of defendants-appellants framed the issues as:
“The primary issues currently in dispute are:
“(1) The degree of permanent partial impairment disability from which claimant is suffering as a result of this alleged accident.
“(2) If he has been found to be disabled, the amount of retraining, if any, due claimant, in addition to the amount heretofore furnished by Employer/Surety.
“(3) That if retraining is found to be available to Claimant under the terms and conditions of Section 72-450,1.C., that such period of retraining be fixed by the Commission, not to exceed 52 weeks, nor to exceed an additional period of 52 weeks, with credit for advances heretofore made by defendants.”
The burden to raise the issue of apportionment is upon defendants-appellants and that failure to raise the issue before the Commission renders inappropriate any review by this Court. Issues not raised below and presented for the first time on appeal will not be considered or reviewed. Silver Syndicate, Inc. v. Sunshine Mining Co., 101 Idaho 226, 611 P.2d 1011 (1979); Frasier v. Carter, 92 Idaho 79, 437 P.2d 32 (1968).
*461Defendants-appellants next argue that the Commission erred in determining the extent of Baldner’s permanent, partial disability by utilizing the difference between Baldner’s pre-injury and post-injury incomes. It is argued that I.C. § 72-425 requires the Commission to consider other factors such as claimant’s age, sex, education, training, usable skills, together with the economic and social environment to determine the extent of a claimant’s permanent disability, and that the Commission’s failure to consider such factors require reversal. We disagree.
I.C. § 72-425 provides:
“Permanent disability evaluation. — ‘Evaluation (rating) of permanent disability’ is an appraisal of the injured employee’s present and probable future ability to engage in gainful activity as it is affected by the medical factor of permanent impairment and by nonmedical factors, such as age, sex, education, economic and social environment, training and usable skills.”
Permanent impairment rating is defined by I.C. § 72-424 as:
“Permanent impairment evaluation— ‘Evaluation (rating) of permanent impairment’ is a medical appraisal of the nature and extent of the injury or disease as it affects an injured employee’s personal efficiency in the activities of daily living, such as self-care, communication, normal living postures, ambulation, elevation, traveling, and nonspecialized activities of bodily members.”
Here Baldner’s permanent partial impairment rating was stated by Dr. Johnson to be equivalent to 15% of the whole man. A claimant’s impairment evaluation or rating is one component or element to be considered by the Commission in determining a claimant’s permanent, partial disability, I.C. § 72-425, and is not the exclusive factor determinative of the disability rating fixed by the Commission. I.C. § 72-427. A disability rating may exceed the claimant’s impairment rating. Paulson v. Idaho Forest Industries, Inc., 99 Idaho 896, 591 P.2d 143 (1979); Murray v. Hecla Mining Co., 98 Idaho 688, 571 P.2d 334 (1977).
I.C. § 72 — 423 defines permanent disability as:
“Permanent disability. — ‘Permanent disability’ or ‘under a permanent disability’ results when the actual or presumed ability to engage in gainful activity is reduced or absent because of permanent impairment and no fundamental or marked change in the future can be reasonably expected.”
See also I.C. §§ 72-102(8) and 72-425.
Our statutes thus make clear, as do our prior cases, that the primary purpose of an award of permanent partial disability benefits is to compensate the claimant for his loss of earning capacity or his reduced ability to engage in gainful activity. Paulson v. Idaho Forest Industries, Inc., 99 Idaho 896, 591 P.2d 142 (1979); Herman v. Sunset Merc. Co., 66 Idaho 47, 154 P.2d 487 (1944); Kelley v. Prouty, 54 Idaho 225, 30 P.2d 769 (1934).
Here, after a detailed recitation of factual findings, the referee’s opinion adopted by the Commission, stated:
“The claimant has ... suffered a loss in earning capacity of $29,821.10 minus $16,-708.63 or $13,112.57 per year, or 44% of his pre-injury wages. Because the claimant’s decrease in wage-earning capacity is equivalent to his decrease in ability to engage in gainful activity in this case, the claimant has suffered a permanent partial disability equal to 44% of a whole man as a result of his back injury. [¶] The Referee recognizes that this is an unusual case. In most cases where a claimant is asserting that his permanent disability exceeds his permanent impairment, he attempts to prove that fact by presenting the testimony of a witness who is an expert in the area of employment. Cf. Murray v. Hecla Mining Company, 98 Idaho 688, 571 P.2d 334 (1977). However, the Workmen’s Compensation Law does not require any particular method of proof. The claimant in this case established a loss of wage-earning capacity as a result of his injury and the *462Referee is convinced that both his pre-injury and post-injury wages accurately represent his ability to engage in gainful activity at the time those wages were earned. Thus, despite the absence of expert testimony, the proof in this case established a loss of ability to engage in gainful activity in excess of the claimant’s impairment rating.” (Emphasis supplied.)
It is clear that the decision was reached upon the correct statutorily mandated basis of “ability to engage in gainful activity”, I.C. § 72-425. We deem the instant case to be unusual in that the claimant, following his impairment and removal from the labor market as an ironworker, has educated and continues to educate, himself for the purpose of finding another line of gainful activity in the labor market. Hence, as stated by the Referee, claimant has demonstrated by actual results, rather than abstract theory, that he has in actuality sustained a decrease in ability to engage in gainful activity. There is no showing on the record that the decision was made without any consideration of factors other than the mathematical comparison of pre-injury and post-injury incomes. It only indicates that the income comparison result measured Baldner’s loss of “ability to engage in gainful activity” accurately regardless, or in spite of, the other factors. We find no error of law, nor do we find the findings lack support in the evidence and hence the Commission’s order will not be set aside. I.C. § 72-732.
Defendants-respondents finally assert that the Commission erred in its determination of Baldner’s total annual pre-injury wages by including therein those earnings from part-time employment, i.e., $5,400 which he earned as an assistant union business agent and from teaching an apprenticeship program. We disagree. I.C. § 72-102(26) provides:
“ ‘Wages’ and ‘wage earning capacity’ prior to the injury or disablement from occupational disease means the employee’s money payments for services as calculated under section 72-419, Idaho Code, and shall additionally include the reasonable market value of board, rent, housing, lodging, fuel, and other advantages which can be estimated in money which the employee receives from the employer as part of his remuneration, and gratuities received in the course of employment from others than the employer. ‘Wages’ shall not include sums which the employer has paid to the employee to cover any special expenses entailed on him by the nature of his employment.”
Defendants-appellants assert that the monies earned by Baldner from such part-time employment are neither board, rent, housing, etc., nor a “gratuity”. Such argument ignores the provisions of I.C. § 72-419(9) which provides:
“When the employee is working under concurrent contracts with two (2) or more employers and the defendant employer has knowledge of such employment prior to the injury, the employee’s wages from all such employers shall be considered as if earned from the employer liable for compensation.”
That statute clearly contemplates the inclusion of a claimant’s earnings from part-time employment in calculating his preinjury wages or income. Here there is no contention that Bennett’s was unaware of Baldner’s two part-time positions. Hence, the earnings from those part-time positions were properly included by the Commission in its determination of Baldner’s total preinjury annual income.
The order of the Industrial Commission is affirmed. Costs to respondent.
McFADDEN and DONALDSON, JJ., concur. BISTLINE, J., concurs in result.