OPINION
WILKINSON, Circuit Judge:Petitioner Grover W. Harris contests the denial of his application for benefits under the Black Lung Benefits Act, 30 U.S.C. § 901 et seq. An administrative law judge determined that Harris’ later employment as a federal mine inspection supervisor was gainful and comparable to his previous work as a mine electrician, and therefore, that Harris did not qualify for benefits. 20 C.F.R. § 727.203(b)(1). In reaching this conclusion, the ALJ compared several different aspects of the jobs, including the skills, abilities, and exertion needed to perform each. Harris argues that in so doing, the ALJ applied an incorrect legal standard for determining what is comparable and gainful employment, and that the evidence in the record does not support the ALJ’s finding. Because we hold that the ALJ applied the appropriate standard and that substantial evidence supports the decision, we affirm 'the judgment.
I.
From 1945 to 1966, Harris worked as a coal miner, usually as a mine electrician. This work involved repairing a variety of electrical, hydraulic, and mechanical equipment, along with the use of a variety of machines and tools. The work required technical knowledge of both the equipment to be fixed and the tools used in making repairs, as well as special skills in working with electricity. According to Harris, the work entailed a lot of lifting, carrying, and working from a variety of cramped positions. He also routinely had to walk, stand, sit, stoop, bend, and kneel.
In 1966, Harris left private employment in the coal mining industry to become a federal mine inspector. In 1978, he advanced to become a federal mine inspection supervisor. In this capacity, Harris oversaw the tasks of an office clerk and five inspectors, including assigning the inspections to be performed and accompanying inspectors into the mines. According to Harris, this job entailed more supervisory skills than being a mine electrician. The job still involved technical knowledge of machinery and electricity, however, and Harris testified that he went underground in the mines two to three times a quarter, occasionally going into “low” coal. The job required walking, standing, sitting, stooping, bending, and kneeling. It also required some crawling and some climbing of ladders. Hams also testified that while in the mines he had to carry a large self-rescuer, a smaller rescuer, a safety light, a methane detector, and various other equipment.
Harris initially filed for black lung benefits with the Social Security Administration in 1973. After his claim was denied administratively by both the SSA and the Department of Labor, Harris eventually sought an administrative hearing, which took place in 1986. The ALJ found that Harris had invoked the interim presumption of total disability due to *105pneumoconiosis, based on x-ray evidence. 20 C.F.R. § 727.203(a)(1). The ALJ then found that Harris’ employment as a federal mine inspection supervisor served to rebut’ the presumption. According to the ALJ, this work required skills, abilities, and physical exertion comparable to being a mine electrician and thus it constituted comparable and gainful work for purposes of rebuttal under § 727.203(b)(1). Accordingly, the ALJ denied Harris’ claim.
Harris appealed to the Benefits Review Board. The Board concluded that substantial evidence supported the ALJ’s decision, and affirmed the denial of benefits. Harris then appealed to this court.
II.
Harris argues that being a federal mine inspection supervisor is in no way comparable to being a mine electrician, and that the ALJ erred in concluding that it was. Harris primarily attacks the ALJ’s factual finding that comparable physical and mental abilities were needed to perform the two jobs. Harris also argues that the ALJ applied the wrong legal standard for determining what is “comparable” work under § 727.-203(b)(1). We disagree with both of these contentions.
A.
First, the ALJ applied the correct legal standard. In his brief, Harris argues that the ALJ improperly applied the standard adopted by the Third Circuit in Echo v. Director, Office of Workers’ Comp. Programs, 744 F.2d 327 (3d Cir.1984). The Third Circuit listed several relevant factors in considering employment comparability, but considered “compensation to be the prime criterion of comparability” because all other factors are “reflected in the level of compensation.” 744 F.2d at 331. Harris contends that instead of relying on compensation, we should adopt the Sixth Circuit’s standard from Ratliff v. Benefits Review Bd., 816 F.2d 1121 (6th Cir.1987). In Ratliff, the Sixth Circuit mentioned comparing skills and abilities, but focused almost exclusively on determining if the two jobs required similar levels of physical exertion. 816 F.2d at 1125.
Our dissenting brother would also make the level of physical exertion the crucial factor. See Discussion in dissenting op. at 109 & 110-11. We think, however, that there are several reasons why the inquiry is more complicated. First, the language of § 727-203(b)(1) does not focus exclusively on the level of physical exertion. The language of “comparable and gainful work” was presumably chosen for a purpose, and courts are not at liberty to elevate a single point of comparability to the detriment of the more generalized inquiry that the regulation’s language plainly invites. Second, a focus solely on physical exertion ignores the fact that persons in later life may choose employment that requires less exertion. Such choices may have everything to do with the general process of aging and little to do with disability from pneumoconiosis. Third, factors other than physical exertion are plainly relevant to the intermediate inquiry on the nature of the employment, as well as to the ultimate legal standard of whether a miner is “totally disabled due to pneumoconiosis.” 30 U.S.C. § 901(a); 20 C.F.R. § 727.201. If a claimant, for example, is able to perform work requiring the exercise of substantial skills and entailing substantial responsibilities, that is at least relevant to, though not necessarily dis-positive of, a disability determination. Fourth, as will be discussed below, the fact-finder did consider physical exertion as an important factor in his analysis, and concluded that Harris was not disabled.
We hold therefore that the proper legal standard for comparing employment under the regulation should include a range of factors, with no single factor assuming paramount importance as a matter of law. This multi-factor standard is a sound one. See Big Horn Coal Co. v. Office of Workers’ Comp. Programs, 897 F.2d 1052, 1056 (10th Cir.1990) (assessing the full range of factors mentioned in Ratliff as well as compensation, and not focusing on a single factor); Pate v. Director, Office of Workers’ Comp. Programs, 834 F.2d 675, 677 (7th Cir.1987) (examining a range of factors and declining to choose one as being of primary importance). As the various cases indicate, the range of *106factors may include compensation, skills and abilities required, levels of exertion, status, responsibility, working conditions, and work location. See Big Horn, 897 F.2d at 1056; Pate, 834 F.2d at 677; Ratliff, 816 F.2d at 1125; Echo, 744 F.2d at 331. Of course, the weight to be assigned a given factor in a particular case is classically within the province of the fact-finder.
In this case, the ALJ undertook such a broad-based factual inquiry, but accorded no undue weight to any one factor. The ALJ considered the technical skills and knowledge required for each job, the specific tasks each entailed, the levels of physical exertion each required, and even the compensation Harris could earn as a federal mine inspection supervisor. There is no indication that the ALJ presumed that petitioner’s other employment around the coal mines precluded petitioner from showing he was totally disabled due to black lung disease. See 30 U.S.C. § 902(f)(1)(B); Ratliff 816 F.2d at 1123. Such an analysis of different factors bearing upon the comparability and gainfulness of employment was a proper application of § 727.203(b)(1). By contrast, making physical exertion the sole determinant distorts results reached under the regulation by focusing on a single aspect of employment to the effective exclusion of the employment experience as a whole.
B.
Harris argues, however, that the evidence at the hearing did not support the ALJ’s finding that the two jobs were comparable. According to Harris, a finding of comparability cannot be supported because being a mine inspection supervisor requires more managerial and supervisory skills but less physical exertion, while being a mine electrician involves strenuous physical labor but no paperwork or supervisory duties. Simply put, because one job is primarily an administrative position spent at a desk and the other entails hours down a mine shaft repairing heavy equipment, the work is completely different.
Our role in the determination of this question is not one of first-instance review. Rather, it simply is to determine whether substantial evidence in the record as a whole supports the ALJ’s decision. See 33 U.S.C. § 921(b)(3) (incorporated into the Black Lung Benefits Act by 30 U.S.C. § 932(a)); 20 C.F.R. § 802.301(a); see also Wilson v. Benefits Review Bd., 748 F.2d 198, 199-200 (4th Cir.1984). “Substantial evidence is ‘such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.’ Richardson v. Perales, 402 U.S. 389, 401 [91 S.Ct. 1420, 1427, 28 L.Ed.2d 842] (1971). While this court must review the entire record, we may neither redetermine the facts nor substitute our own judgment for that of the ALJ.” Freeman United Coal Mining Co. v. Benefits Review Bd., 919 F.2d 451, 452 (7th Cir.1990).
The dissent does acknowledge the appropriate standard of review. It then proceeds, however, to redetermine the issue from ground zero. Such reweighing of the evidence is an exercise in de novo review, not a substantial evidence inquiry. Factfinders exist for definite purposes, one of which is to observe the demeanor of claimants whose testimony is frequently the only live testimony at the hearing. Appellate courts are well-positioned to determine whether a factual finding is without support in the evidence; we are much less able simply to overturn a factfinder on a question on which two views of the evidence are possible. Regrettably, the dissent has attempted this last feat, and in so doing has read the record before the ALJ to accentuate differences and downplay similarities between Harris’ private and government employment. For example, while the dissenting opinion notes that the claimant’s “Work Activity Development Worksheet” with its parallel columns for comparing physical activities was submitted into evidence, dissenting op. at 110 n. 3, it omits the fact that Harris himself indicated on the form that both jobs required walking, standing, sitting, stooping, bending, and kneeling. Plainly, this description is something the ALJ could consider in finding comparability. The dissent also challenges the ALJ’s factual findings of the government job requiring “a great deal of walking” and “occasional crawling” by focusing on the claimant’s oral testimony about when he walked and crawled in the mines, id. at 110 n. 3 & 111, but minimiz*107ing Harris’ statement on the form that his government job entailed a “lot of walking [and] crawling.” Factfinders routinely resolve discrepancies between evidentiary sources, and by being able to observe testimony first-hand, they are in the best position to do so. The dissenting opinion thus serves to illustrate the special hazards of attempting first-instance fact finding in the course of an appeal. In taking one view of the evidence, the dissent ignores the fact that other views are at the very least quite plausible. Indeed, the real import of the dissent’s position is that any job with substantial office or supervisory responsibilities cannot be comparable to previous mine employment as a matter of law. We think it risky, however, to resolve individualized disability determinations of this sort in such categorical terms.
Rather, we agree with the Director and the other circuits that disability, specifically here rebuttal of an interim presumption of disability, should be determined as a factual matter, and that the deference mandated by the standard of review should apply. In this case, substantial evidence supports the ALJ’s finding that the two jobs were comparable. Evidence in the record indicates that the jobs of federal mine inspection supervisor and mine electrician shared significant attributes. Both jobs required a technical knowledge of coal mine machinery, electricity, and their use in the mines. As an electrician, Harris had to use and repair a wide variety of mining equipment; as an inspection supervisor, he had to know about and use even more types of mine safety and rescue equipment. From this evidence, the ALJ certainly could find, as he did, that Harris “was skilled in using various machines at both jobs,” and that both jobs “required technical knowledge.” This carry over of knowledge about coal mines and mining machinery and equipment indicates comparability. As the Director notes, Harris himself made a conscious decision upon leaving private employment to pursue a government job that drew upon the skills and experience obtained during his twenty-one years in the mines.
Harris’ work as a federal mine inspection supervisor also required physical effort. Harris testified that he continued to enter the mines a couple of times each quarter, and that the job still required him to crawl through low coal. Being an inspection supervisor also did not relieve Harris of the obligation to carry certain types of equipment with him into the mines. The ALJ’s listing of this “heavy and cumbersome equipment” included large self-rescuers, safety lights, and methane detectors. As we have noted, Harris’ own description of the physical activities of each job indicated that both required many of the same physical activities, including walking, standing, sitting, stooping, bending, and kneeling, with the government job requiring even more climbing of ladders than the electrician position. This evidence of exertion, along with the evidence of comparable skills and knowledge, supported the ALJ’s finding of § 727.208(b)(1) rebuttal.*
It may be readily conceded, as the Director has, that Harris spent less time in the mines, lifted less heavy equipment, and exerted himself less as a mine inspection supervisor than as a mine electrician. To focus purely on exertion level, however, is to accede to the single factor inquiry that we have earlier rejected. The two jobs should be assessed along a variety of different grounds by a fact-finder in the best position to compare the overall circumstances of employment. Obviously, the positions of federal mine inspection supervisor and mine electrician are not an exact match, but they need not be; - “the statute requires comparability, not identity.” Pate, 834 F.2d at 677. Given this standard, there is plainly substantial evidence in the record to support the ALJ’s determination.
*108III.
In sum, we uphold the finding that petitioner’s employment as a federal coal mine inspection supervisor rebutted the interim presumption of total disability due to pneu-moconiosis. For the above reasons, the decision of the Benefits Review Board is
AFFIRMED.
Testimony in the record gave Harris’ salary as a federal mine inspection supervisor as $48,000 in 1986. While the ALJ noted only that Harris could "earn full pay at his current job,” salary comparison would have been difficult given the twenty-year time lapse since Harris earned $11,-000 as a mine electrician and the lack of any definitive evidence before the ALJ on 1986 wages for mine electricians. Still, the testimony about Harris' salary and benefits in his government job certainly indicated that it was gainful employment under § 727.203(b)(1), and that the ALJ appropriately considered this factor.