concurring.
Because I agree that Mr. Dorrough is not entitled to a reduction in his sentence, I concur in the judgment of the court, although I do so on a ground unrelated to the P2P quantity. I write separately, however, to express my disagreement with the majority’s conclusions regarding the retroactive application of Amendment 484 in this case.
The majority opinion assumes the district court decided not to give Amendment 484 retroactive application “after considering the relevant factors” set forth at 18 U.S.C. § 3553(a). The record before us, however, does not provide such a clear picture of the district court’s reasoning. Indeed, at first glance, it appears the district court did in fact apply the amendment retroactively. The court adopted by reference the Second Addendum to the Presentence Report, which purported to calculate Mr. Dorrough’s sentence “in accordance with the guideline manual in effect November 1, 1994.” Because Amendment 484 became effective November 1,1993, the sentencing court’s use of the 1994 version of the guideline manual would indicate that the court at least attempted to apply the amendment retroactively. The majority opinion appears to acknowledge this possibility. See ante at 1311 (“[T]he sentencing court reviewed Mr. Dorrough’s sentence in light of Amendment 4,84,....”) (emphasis added).
However, the outcome reached by the district court suggests that the court did not apply the amendment retroactively, or if it did do so, that it erred in its application of the amendment. The district court stated that it was calculating Mr. Dorrough’s sentence based on the entire 91 liter mixture containing P2P, even though Amendment 484 explicitly directs a sentencing court to exclude from the drug quantity calculation those “materials that must be separated from the controlled substance before the controlled substance can be used.” U.S.S.G. § 2D1.1, comment, (n.l). Because, the 91 liter chemical mixture was seized from Mr. Dorrough’s laboratory before processing was completed, no one disputes that it would have been necessary to separate the various chemical by-products from the mixture before the P2P then in the solution could be used for its intended purpose of manufacturing amphetamine. See United States Sentencing Commission, Guideline Manual, App. C., amend. 484 (“The chemicals seized before the end of processing are also not usable in that form because further processing must take place before they can be used.”). If the nature of the lab mixture was such that the usable and nonusable materials could not be separated, then Amendment 484 required the district court “to use any reasonable method to approximate the weight of the” P2P in the mixture. U.S.S.G. § 2D1.1, comment, (n.1).1 Thus, if the district court was attempting to apply Amendment 484, I believe the court erred in calculating Mr. Dorrough’s sentence based on the entire 91 liter mixture containing P2P, rather than the actual amount of P2P therein. See United States v. Deninno, 29 F.3d 572, 579 (10th Cir.1994) (“[T]he full amount of the waste water need not be used in the calculation of quantity of the [controlled substance].”), cert. denied, — U.S. -, 115 S.Ct. 1117, 130 L.Ed.2d 1081 (1995); United States v. Levay, 76 F.3d 671, 673 (5th Cir.1996) (“Under the amended guideline, only the actual weight of the controlled substance is applied in calculating the base offense level, not the aggregate weight of any mixture_”).
The ambiguity regarding whether the district court in fact applied Amendment 484 retroactively merely underscores a more obvious judgment that can be drawn from the district court’s opinion, which is that the district court in any event failed to undertake a proper retroactivity analysis. As the ma*1313jority correctly observes, whether to give retroactive application to a guideline amendment is a decision that rests within the discretion of the district court after the court evaluates the factors set forth at 18 U.S.C. § 3553(a). Although we have stated in another context that a sentencing court need not “make specific findings relating to each of the [§ 3553(a) ] factors considered,” United States v. Lee, 957 F.2d 770, 774-75 (10th Cir.1992) (addressing the factors in connection with a challenge to the revocation of supervised release under § 3583), the sentencing court nevertheless remains obligated to state clearly the reasons for its decision. Id. In many other sentencing areas, we have required district courts to make explicit findings of fact to support their sentence calculations. See, e.g., United States v. Roberts, 14 F.3d 502, 522 (10th Cir.1993) (“In enhancing a defendant’s sentence based on his role in the offense, a district court must make specific factual findings as to that role.”); United States v. Molina-Cuartas, 952 F.2d 345, 348 (10th Cir.1991) (“In order to impose a sentence based on a quantity of drugs, the trial court's factual findings must be determined by a preponderance of the evidence.”), cert. denied, 503 U.S. 995, 112 S.Ct. 1698, 118 L.Ed.2d 408 (1992). I see no reason why consideration of a sentence reduction under § 3582(c), which specifically directs the district court to consider the factors set forth in § 3553(a), should be treated any differently. As an appellate court we are always hindered, and often completely prevented, from effectively reviewing the district court’s exercise of sentencing discretion if the district court fails to address the statutorily-mandated factors that Congress has said should direct and guide that discretion.
In any event, even if we were not to require the sentencing court to address explicitly the statutory factors, at a very minimum we require the sentencing court to “state the reasons for its action,” Lee, 957 F.2d at 775, and it goes without saying that the reasons provided by the court must have some correlation to the statutory factors set forth in § 3553(a), see United States v. Avila, 997 F.2d 767, 768 (10th Cir.1993) (holding that the district court’s power to reduce a sentence in light of a subsequent amendment to the guidelines “is tethered to the factors contained in § 3553(a)”). In my opinion, the district court in this case has failed to comply with even this minimal requirement. The district court’s order makes no reference to § 3553(a), nor do any of the court’s stated reasons for denying Mr. Dorrough’s sentence reduction bear any relation to the criteria set forth in § 3553(a). At one point, the district court did rely on the fact that the sentencing guidelines “take into account a percentage of waste in P2P, evidenced by the sizeable decrease in drug equivalency ratios.” R.O.A. Yol. X, p. 7. While this statement may be interpreted as reflecting the district court’s concern about sentencing disparities, see 18 U.S.C. § 3553(a) (directing sentencing courts to consider, inter alia, “the need to avoid unwarranted sentence disparities among defendants”), I do not believe it is a correct statement of the law.
The decreased drug equivalency ratio between amphetamine and P2P cannot be explained on the basis of accounting for “waste” associated with P2P. The drug equivalency ratio remains constant throughout the manufacturing process and yet the amount of “waste” associated with the P2P is much greater earlier in the manufacturing process than it is late in the process. That is, as I understand it, the P2P becomes more concentrated in the mixture as it is being manufactured. Thus, under the district court’s interpretation of the guidelines, a defendant is punished more severely earlier in the manufacturing process (when the P2P is more diluted and less usable) than he is later in the process when the manufacturing is complete and the P2P is pure. Contrary to the district court’s suggestion, I believe P2P is punished less severely than amphetamine simply because it is not as dangerous a controlled substance. P2P is not an ingestible drug, and additional ingredients must be chemically combined with it in order to manufacture the finished amphetamine product.
Finally, when the § 3553(a) factors are addressed, I am led to conclude that it would be an abuse of discretion to hold that Amendment 484 does not apply retroactively in this case. The factors set forth in § 3553(a) are the following: (1) the nature and circum*1314stances of the offense and the history and characteristics of the defendant; (2) the need for the sentence imposed; (3) the kinds of sentences available; (4) the applicable sentencing range under the guidelines; (5) any pertinent Sentencing Commission policy statement; (6) the need to avoid unwarranted sentence disparities among defendants; and (7). the need to provide restitution to victims. 18 U.S.C. § 3553(a). Applied to Mr. Dorrough’s ease, I believe the first four factors and the seventh factor are either neutral or irrelevant. The district court emphasized that the nature and circumstances of the offense involved a clandestine laboratory engaged in the process of manufacturing amphetamines. However, because all illegal drug labs manufacture illegal substances and are presumably clandestine, it is difficult to understand how this supports a finding against retroactivity. The sixth factor actually supports applying Amendment 484 retroactively; a defendant sentenced under the pre-Amendment 484 guidelines could receive a much harsher sentence for precisely the same conduct as a defendant sentenced after the effective date of Amendment 484. See, e.g., United States v. Levay, 76 F.3d 671, 673 (5th Cir.1996) (noting that application of Amendment 484 would reduce that particular defendant’s base offense level by 20 points). The fifth factor also may support retroactivity because the fact that U.S.S.G. § lB1.10(c) includes Amendment 484 in relatively select company of guideline amendments that may be applied retroactively suggests perhaps some threshold presumption of retroactivity.
While I part with the majority’s conclusions regarding the retroactivity and Amendment 484 issues, I nevertheless concur in the judgment. The Second Addendum to the Presentence Report, which the district court adopted by reference into its order, offers an alternative (and I believe a correct) method for sentencing Mr. Dorrough that results in a sentence identical to that originally imposed. The sentencing guidelines provide that “[i]f the offense involved both a substantive drug offense and an attempt or conspiracy, the total quantity involved shall be aggregated to determine the scale of the offense.” U.S.S.G. § 2D1.1, comment, (n.12) (parenthetical omitted). Further, where the amount of drugs seized does not reflect the scale of the offense, the guidelines direct the sentencing court to “approximate the quantity of the controlled substance ... consider[ing], for example, ... the size or capability of any laboratory involved.” Id.; see also United States v. Sturmoski, 971 F.2d 452, 456, 462 (10th Cir.1992) (estimating drug quantity based on the capability of the laboratory and the amount of precursor chemicals seized); United States v. Short, 947 F.2d 1445, 1456-57 (10th Cir.1991) (estimating drug quantity based on characteristics of drug laboratory), cert. denied, 503 U.S. 989, 112 S.Ct. 1680, 118 L.Ed.2d 397 (1992). Because Mr. Dorrough was convicted of attempt and conspiracy to manufacture amphetamine (in addition to possession of P2P), he may be sentenced for the approximate amount of amphetamine he intended to manufacture. At the original sentencing hearing, the government criminalist testified that Mr. Dorrough’s laboratory was capable of producing approximately 100 pounds of amphetamine. See Second Addendum to Presentence Report. Based on this estimate, Mr. Dorrough would still have been assigned a base offense level of 34 under U.S.S.G. § 2D1.1(c)(3). For this reason, I do not believe Mr. Dorrough is entitled to a reduced sentence and thus I concur in the judgment of the court.
. Mr. Dorrough presented the district court with a reasonable method of approximating the amount of-P2P in the mixture; namely, a chemist who testified that the chemicals seized from Mr. Dorrough's laboratory cotdd have produced at most 8.85 kilograms, or 19.5 pounds, of P2P.