DefendanL-Appellant Gerard Cavera appeals from a judgment entered on August 23, 2005 in the United States District Court for the Eastern District of New York.1 Cavera pled guilty to a firearms trafficking offense. The district court imposed an above-Guidelines sentence after finding that the Sentencing Guidelines failed to take into account the need to punish more severely those who illegally transport guns into areas like New York City. On appeal, Cavera contends, among other things, that the district court erred when it relied on local conditions to justify a higher sentence.
A panel of this Court held that the district court rested its decision on impermissible considerations, and determined that the sentence should be vacated and the case remanded for resentencing. United States v. Cavera, 505 F.3d 216 (2d Cir. 2007). We ordered rehearing en banc, and directed the parties to submit briefs on the effect of the Supreme Court’s intervening decisions in Gall v. United States, — U.S. -, 128 S.Ct. 586, 169 L.Ed.2d 445 (2007), and Kimbrough v. United States, — U.S.-, 128 S.Ct. 558, 169 L.Ed.2d 481 (2007). With the benefit of the guidance afforded by those rulings, we now affirm the 10 judgment of the district court.
[185] I.
Cavera, a septuagenarian army veteran with residences in New York and Florida, was arrested by the FBI with the aid of a confidential informant. Beginning in July 2003, the informant purchased guns illegally in New York City on several occasions from a man named Peter Abbadessa. Ab-badessa told the confidential informant that his uncle, Anthony Lucania, had a friend named Gerry (Cavera), who acted as Abbadessa’s Florida gun supplier. In April 2004, the confidential informant flew to Florida, along with Abbadessa and Lu-cania, for the express purpose of procuring firearms. At the FBI’s direction, the informant paid Lucania $11,500 for sixteen guns. Abbadessa and Lucania then went to Cavera’s residence in Deerfield Beach, Florida, where they gave Cavera money in exchange for two boxes containing sixteen firearms. The boxes were later given to the informant, who turned them over to the FBI. Abbadessa, Lucania, and the confidential informant returned to New York on separate flights.
On June 23, 2004, a grand jury returned an indictment charging Cavera, Abbades-sa, and Lucania with various violations of the federal gun trafficking laws. Cavera pled guilty to one count of conspiracy to deal in and to transport firearms, in violation of 18 U.S.C. § 371.
Cavera first appeared for sentencing on June 9, 2005. At this point, Judge Sifton gave notice that he was considering an above-Guidelines sentence, “simply because I think the sentencing guidelines may understate the seriousness of this offense because of the consequences for the community of bringing or transporting ... firearms into New York City.” To guide the parties, Judge Sifton referred them to articles written by himself and by then-District Judge Raggi on local variation in federal sentencing. See Charles P. Sifton, Theme and Variations: The Relationship Between National Sentencing Standards and Local Conditions, 5 Fed. Sent’g Rep. 303 (1993); Reena Raggi, Local Concerns, Local Insights: Further Reasons for More Flexibility in Guideline Sentencing, 5 Fed. Sent’g Rep. 306 (1993). The district court adjourned the proceedings to give the parties an opportunity to address the issue.
The parties appeared again for sentencing on July 28, 2005. The court determined that the Guidelines recommended a sentence of twelve to eighteen months’ imprisonment and a fine of $3,000 to $30,000. But Judge Sifton concluded that a higher sentence was appropriate, stating in open court that the Guidelines range did not adequately meet the “crying need to do what can be done to deter gun trafficking into the large metropolitan area[s] of this country.” At the same time, the district court filed a detailed written opinion further explaining its reasoning. United States v. Lucania, 379 F.Supp.2d 288 (E.D.N.Y.2005).
In this opinion, Judge Sifton began by noting that the Guidelines, “[i]n the pursuit of national uniformity in sentencing practices,” do not take local circumstances into account, and instead reflect a national average. Id. at 293-94. For this reason, the Guidelines were “less persuasive” in Cavera’s case than they would otherwise be. Id. at 296.
The district court explained its decision to impose an above-Guidelines sentence in terms of two of the § 3553(a) factors. Focusing first on the need for the sentence to reflect the seriousness of the offense, as directed by 18 U.S.C. § 3553(a)(2)(A), Judge Sifton found that Cavera’s offense was more harmful than the national average offense contemplated by the Guidelines. “Firearms smuggled into New York City commonly end up in the hands of [186] those who could not otherwise legally acquire them, are frequently used for illegitimate purposes, and have the potential to create a substantially greater degree of harm when in an urban environment ... than in the United States generally.” Im-cania, 379 F.Supp.2d at 295.2 In this respect, the district court referred to statistical studies indicating that homicide rates were substantially higher in large urban areas than in suburban and rural locales. Id. Judge Sifton also noted that population density in the state of New York, in New York City, and especially in particular parts of the Eastern District of New York, exceeded the national average. Id. at 295 n. 3.
The district court also relied on a greater-than-average need, in this case, to achieve strong deterrence. See 18 U.S.C. § 3553(a)(2)(B). The purpose of gun trafficking laws “is to prevent lax firearm laws in one state from undermining the more restrictive laws of other states.” Lucania, 379 F.Supp.2d at 295. In states with strict gun laws, like New York, a higher percentage of guns used in crimes arrive from out of state than is the case in jurisdictions with less restrictive firearms laws. New York’s strict gun control laws create a “larger black market” for guns than in places with less strict laws. Id. The district court cited an article describing New York City as “one of the ‘unusual areas’ to which running guns is a profitable enterprise.” Id. (citing Gary Kleek, BATF Gun Trace Data and the Role of Organized Gun Trafficking in Supplying Guns to Criminals, 18 St. Louis Univ. Pub.L.Rev. 23, 41 (1999)). Accordingly, Judge Sifton concluded that a more severe penalty for trafficking guns into New York City was necessary to bring about adequate deterrence. Lucania, 379 F.Supp.2d at 295-96.
The district court noted next that a sentencing judge is also directed to consider “the need to avoid unwarranted sentencing disparities among defendants with similar records who have been found guilty of similar conduct.” 18 U.S.C. § 3553(a)(6). Judge Sifton recognized that his approach would lead to different sentences for otherwise-similar firearms traffickers in different federal districts. Such disparities, however, were not “unwarranted.” Luca-nia, 379 F.Supp.2d at 296. Rather, they were based on “objectively demonstrated, material differences between the impact of the offenses in those districts.”3 Id.
In one respect, Cavera benefited from Judge Sifton’s willingness to disagree with the Guidelines. Judge Sifton noted that the Guidelines also failed to take into account “the inverse relationship between age and recidivism.” Id. at 298. Judge Sifton stated that he would consider the lesser need for specific deterrence when sentencing Cavera, who was over seventy. Id. at 297-98.
On these bases, the court imposed a sentence of twenty-four months’ imprisonment — six months longer than the top end of the applicable Guidelines range. Cav-era was also sentenced to three years’ supervised release, a $60,000 fine, and a $100 special assessment.
Cavera appealed the sentence. Initially, the Government agreed with Cavera that the sentence could not stand.4 Writing [187] before Gall and Kimbrough, a panel of this Court held that Judge Sifton erred in his analysis of the § 3558(a) factors “by sentencing Cavera on the basis of a policy judgment concerning the gravity of firearms smuggling into a heavily populated area, like New York City, rather than on circumstances particular to the individual defendant and his crime.” Cavera, 505 F.3d at 222 (citing United States v. Rattoballi, 452 F.3d 127, 133 (2d Cir.2006)). For this reason, the panel determined that the sentence was procedurally and substantively unreasonable. Id. at 225. A majority of the Court’s active judges voted to rehear the case en banc. See Fed. R.App. P. 35(a).
II.
This Court employs the en banc procedure sparingly. But when we do hear a case en banc, and we are in substantial agreement, an en banc opinion gives us the opportunity to speak somewhat more broadly, for the purpose of giving guidance to district courts in this Circuit and to future panels of this Court, than we normally do as individual panels. Of Jon O. Newman, In Banc Practice in the Second Circuit: The Virtues of Restraint, 50 Brook. L.Rev. 365, 382 (1984) (“[A]n occasional in banc decision is useful to provide guidance in a frequently litigated area of the law....”). Conversely, where our members possess significantly differing views on a particular issue, it is often wise to avoid speaking as an en banc Court unless the point is one that is strictly necessary to decide the case. See Jon O. Newman, In Banc Practice in the Second Circuit, 1984-1988, 55 Brook. L.Rev. 355, 369 (1989) (“[FJrequent use of the in banc practice surely poses a threat to [collegiality].”). The case before us presents issues of both sorts.
A.
In United States v. Booker, the Supreme Court held that the mandatory application of the Sentencing Guidelines was incompatible with the Sixth Amendment. 543 U.S. 220, 226-27, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). Accordingly, the Court excised the portion of the Sentencing Reform Act of 1984 that ordinarily required district courts to impose Guidelines-range sentences. See id. at 245-46, 125 S.Ct. 738 (Remedial Op., Breyer, J.); see also 18 U.S.C. § 3553(b)(1). In Justice Breyer’s “Remedial Opinion,” the Court retained an important role for the Sentencing Commission, -leaving untouched the statutory direction to district courts that they should consult the Guidelines range when imposing sentence. See Booker, 543 U.S. at 245-46,125 S.Ct. 738 (Remedial Op., Breyer, J.); see also 18 U.S.C. § 3553(a). Booker rendered the Guidelines “effectively advisory,” and permitted sentencing courts to tailor the appropriate punishment to each offense in light of other concerns. 543 U.S. at 245, 125 S.Ct. 738 (Remedial Op., Breyer, J.). After Booker, appellate courts were to review sentences for “unreasonableness.” Id. at 261, 125 S.Ct. 738. (Remedial Op., Breyer, J.) (internal quotation marks and alteration omitted). Review for “unreasonableness” amounts to review for abuse of discretion. See Gall, 128 S.Ct. at 594 (“Our explanation of ‘reasonableness’ review in the Booker opinion made it pellucidly clear that the familiar abuse-of-discretion standard of review now applies to appellate review of sentencing decisions.”); Kim-brough, 128 S.Ct. at 576 (“The ultimate question in Kimbrough’s case is ‘whether the sentence was reasonable — i.e., whether the District Judge abused his discretion in determining that the § 3553(a) factors supported a sentence of [15 years] and justified a substantial deviation from the Guidelines range.’ ”) (quoting Gall, 128 [188] S.Ct. at 600); see also United States v. Fernandez, 443 F.3d 19, 27 (2d Cir.2006) (stating that reasonableness review is “akin to review for abuse of discretion”).5
The resulting regime is, at first glance, beguilingly simple. The district courts have discretion to select an appropriate sentence, and in doing so are statutorily bound to consider the factors listed in § 3553(a), including the advisory Guidelines range. The courts of appeals then review for abuse of discretion.
Booker, however, left unanswered a number of questions, both for sentencing judges and for those charged with the task of reviewing their work on appeal. Two of these are of particular relevance to this case. One question especially relevant to sentencing judges is to what extent may a district court, consistent with its statutory duty to consider the Guidelines, base its sentence on a policy disagreement with the Sentencing Commission? The second question, especially relevant to courts of appeals, is to what extent must appellate courts defer to the decisions of district courts? As Judge Henry Friendly presciently noted, abuse of discretion is not a uniform standard of review. Henry J. Friendly, Indiscretion About Discretion, 31 Emory L.J. 747, 756 (1982). Rather, where an appellate court reviews for abuse of discretion, “ ‘the scope of review will be directly related to the reason why the category or type of decision is committed to the trial court’s discretion in the first instance.’ ” Id. at 764 (quoting United States v. Criden, 648 F.2d 814, 817 (3d Cir.1981)). “[Djefining the proper scope of review of trial court determinations requires considering in each situation the benefits of closer appellate scrutiny as compared to those of greater deference.” Id. at 756. In the sentencing context, the question is further complicated by the presence of a third institution, the Sentencing Commission. The Supreme Court recently offered further guidance. See Gall v. United States, — U.S. -, 128 S.Ct. 586, 169 L.Ed.2d 445 (2007); Kimbrough v. United States, — U.S. --, 128 S.Ct. 558, 169 L.Ed.2d 481 (2007); Rita v. United States, 551 U.S. 338, 127 S.Ct. 2456, 168 L.Ed.2d 203 (2007). In these cases, the Court expressed its view of the respective competencies of the Sentencing Commission, the district judges, and the courts of appeals. In some respects, the Supreme Court’s recent decisions require us to modify our own practices. From those opinions, and from our own experience with the advisory Guidelines system, we derive the following principles.
A sentencing judge has very wide latitude to decide the proper degree of punishment for an individual offender and a particular crime. In addition to taking into account the Guidelines range, the district court must form its own view of the “nature and circumstances of the offense and the history and characteristics of the defendant.” 18 U.S.C. § 3553(a)(1). The sentencing judge is directed, moreover, to consider: a) the need to reflect the seriousness of the offense, to promote respect for the law, and to provide just punishment for that offense; b) the need to afford adequate deterrence to criminal conduct; c) the need to protect the public from further crimes by the defendant; and d) the need for rehabilitation. Id. § 3553(a)(2). Additionally, district courts must take into account: the kinds of sentences available, id. § 3553(a)(3); any per[189] tinent Sentencing Commission policy statement, id. § 3553(a)(5); the need to avoid unwarranted sentence disparities among similarly situated defendants, id. § 3553(a)(6); and, where applicable, the need to provide restitution to any victims of the offense, id. § 3553(a)(7).
Even after Gall and Kimbrough, sentencing judges, certainly, are not free to ignore the Guidelines, or to treat them merely as a “body of casual advice.” See United States v. Crosby, 397 F.3d 103, 113 (2d Cir.2005). A district court should normally begin all sentencing proceedings by calculating, with the assistance of the Pre-sentence Report, the applicable Guidelines range. Gall, 128 S.Ct. at 596; see also Crosby, 397 F.3d at 112 (describing situations in which “precise calculation of the applicable Guidelines range may not be necessary”). The Guidelines provide the “starting point and the initial benchmark” for sentencing, Gall, 128 S.Ct. at 596, and district courts must “remain cognizant of them throughout the sentencing process,” id. at 596 n. 6. It is now, however, emphatically clear that the Guidelines are guidelines — that is, they are truly advisory. A district court may not presume that a Guidelines sentence is reasonable;6 it must instead conduct its own independent review of the sentencing factors, aided by the arguments of the prosecution and defense. District judges are, as a result, generally free to impose sentences outside the recommended range. When they do so, however, they “must consider the extent of the deviation and ensure that the justification is sufficiently compelling to support the degree of the variance.” Id. at 597. In this way, the district court reaches an informed and individualized judgment in each case as to what is “sufficient, but not greater than necessary” to fulfill the purposes of sentencing. 18 U.S.C. § 3553(a).
After Gall and Kimbrough, appellate courts play an important but clearly secondary role in the process of determining an appropriate sentence. We review the work of district courts under a “deferential abuse-of-discretion standard.” Gall, 128 S.Ct. at 591. This form of appellate scrutiny encompasses two components: procedural review and substantive review.
As to substance, we will not substitute our own judgment for the district court’s on the question of what is sufficient to meet the § 3553(a) considerations in any particular case. See United States v. Fernandez, 443 F.3d 19, 27 (2d Cir.2006). We will instead set aside a district court’s substantive determination only in exceptional cases where the trial court’s decision “cannot be located within the range of permissible decisions.” United States v. Rigas, 490 F.3d 208, 238 (2d Cir.2007) (internal quotation marks omitted). To the extent that our prior cases may be read to imply a more searching form of substantive review, we today depart from that understanding. See, e.g., United States v. Cutler, 520 F.3d 136, 164, 167 (2d Cir.2008).7
This degree of deference is only warranted, however, once we are satisfied that the district court complied with the Sentencing Reform Act’s 'procedural requirements, and this requires that we be confident that the sentence resulted from [190] the district court’s considered judgment as to what was necessary to address the various, often conflicting, purposes of sentencing. See In re Sealed Case, 527 F.3d 188, 191 (D.C.Cir.2008) (“Given the broad substantive discretion afforded to district courts in sentencing, there are concomitant procedural requirements they must follow.”).
A district court commits procedural error where it fails to calculate the Guidelines range (unless omission of the calculation is justified, see Crosby, 397 F.3d at 112), makes a mistake in its Guidelines calculation, or treats the Guidelines as mandatory. Gall, 128 S.Ct. at 597. It also errs procedurally if it does not consider the § 3553(a) factors, or rests its sentence on a clearly erroneous finding of fact. Id. Moreover, a district court errs if it fails adequately to explain its chosen sentence, and must include “an explanation for any deviation from the Guidelines range.”8 Id. Where we find significant procedural error, one proper course would be to remand to the district court so that it can either explain what it was trying to do, or correct its mistake and exercise its discretion anew, see, e.g., United States v. Williams, 524 F.3d 209, 215-17 (2d Cir. 2008), rather than for the appellate court to proceed to review the sentence for substantive reasonableness. See Gall, 128 S.Ct. at 597 (“Assuming that the district court’s sentencing decision is procedurally sound, the appellate court should then consider the substantive reasonableness of the sentence imposed under an abuse-of-discretion standard.” (emphasis added)).
These broad statements, however, require more specificity, both as to substantive and procedural reasonableness
review if they are to guide us in particular cases, including the one before us. Thus, when conducting substantive review, we take into account the totality of the circumstances, giving due deference to the sentencing judge’s exercise of discretion, and bearing in mind the institutional advantages of district courts. Rita, 127 S.Ct. at 2466-67 (“In sentencing, as in other areas, district judges at times make mistakes that are substantive .... Circuit courts exist to correct such mistakes when they occur.”). Unlike some of our sister circuit courts, we do not presume that a Guidelines-range sentence is reasonable. Fernandez, 443 F.3d at 27; see Rita, 127 S.Ct. at 2462 (permitting, but not requiring, the courts of appeals to adopt a presumption of reasonableness for within-Guidelines sentences); see also Gall, 128 S.Ct. at 597 (“If the sentence is within the Guidelines range, the appellate court may, but is not required to, apply a presumption of reasonableness”). Nor can we presume that a non-Guidelines sentence is unreasonable, or require “extraordinary” circumstances to justify a deviation from the Guidelines range. Gall, 128 S.Ct. at 595. Where, as in the case before us, we review a non-Guidelines sentence, we may “take the degree of variance into account and consider the extent of a deviation from the Guidelines.” Id. But we must not employ a “rigid mathematical formula that uses the percentage of a departure as the standard for determining the strength of the justifications required for a specific sentence.” Id.
In reviewing sentences for reasonableness, we are, of course, bound by 18 U.S.C. § 3661. (stating that “[n]o limitation shall be placed on the information concerning the background, character, and
[191] conduct of a person convicted of an offense which a court of the United States may receive and consider for the purpose of imposing an appropriate sentence”). Thus, at the procedural part of review, we will not categorically proscribe any factor “concerning the background, character, and conduct” of the defendant, with the exception of invidious factors. See, e.g., United States v. Kaba, 480 F.3d 152, 156— 57 (2d Cir.2007); see also United States v. Watts, 519 U.S. 148, 152, 117 S.Ct. 633, 136 L.Ed.2d 554 (1997) (citing § 3661 in concluding that reviewing courts cannot “invent a blanket prohibition against considering certain types of evidence at sentencing”); United States v. Concepcion, 983 F.2d 369, 387 (2d Cir.1992) (recognizing sentencing court’s authority to “take into account any information known to it”). But this does not grant district courts “a blank check to impose whatever sentences suit their fancy.” . United States v. Jones, 531 F.3d 163, 174 (2d Cir.2008). At the substantive stage of reasonableness review, an appellate court may consider whether a factor relied on by a sentencing court can bear the weight assigned to it. To be sure, this review is deferential. See Gall, 128 S.Ct. at 597 (holding that appellate court “must give due deference” to the district court’s determination as to the “extent” of variance warranted by a given factor). As a result, we do not consider what weight we would ourselves have given a particular factor. Id. Rather, we consider whether the factor, as explained by the district court, can bear the weight assigned it under the totality of circumstances in the case. Such an approach is consistent with and follows from the Supreme Court’s emphasis on “individualized” sentencing, id., because it allows district courts to explain why factors that might not be relevant in most cases are relevant in the case at issue. At the same time, it ensures that appellate review, while deferential, is still sufficient to identify those sentences that cannot be located within the range of permissible decisions.
Accordingly, we will continue to patrol the boundaries of reasonableness, while heeding the Supreme Court’s renewed message that responsibility for sentencing is placed largely in the precincts of the district courts. In at least one respect, Gall and Kimbrough manifestly require us to give more latitude to sentencing judges than this Court did before. After the Supreme Court’s decision in Booker but before its decisions in Kimbrough and Gall, we suggested that it was not permissible for a district court to rest its decision on a policy judgment applicable to an entire category of offenses. See, e.g., Cavera, 505 F.3d at 223; United States v. Trupin, 475 F.3d 71, 76 (2d Cir.2007), vacated, — U.S. -, 128 S.Ct. 862, 169 L.Ed.2d 711 (2008); United States v. Park, 461 F.3d 245, 249 (2d Cir.2006); United States v. Castillo, 460 F.3d 337, 361 (2d Cir.2006), abrogated by Kimbrough, — U.S. -, 128 S.Ct. 558, 169 L.Ed.2d 481; cf. United States v. Wills, 476 F.3d 103, 109 (2d Cir.2007); United States v. Rattoballi, 452 F.3d 127, 133 (2d Cir.2006). That, we now know, is not the case. As the Supreme Court strongly suggested in Kimbrough, a district court may vary from the Guidelines range based solely on a policy disagreement with the Guidelines, even where that disagreement applies to a wide class of offenders or offenses. See Kimbrough, 128 S.Ct. at 574-75; see also United States v. Regalado, 518 F.3d 143, 147 (2d Cir. 2008).
When, moreover, we examine a district court’s justification for differing from the Guidelines recommendation, our review must be informed by the “discrete institutional strengths” of the Sentencing Commission and the district courts. Kim-[192] brough, 128 S.Ct. at 574.9 As a result, a district court’s decision to vary from the Guidelines “may attract greatest respect when the sentencing judge finds a particular case outside the ‘heartland’ to which the Commission intends individual Guidelines to apply.” Id. at 574-75 (internal quotation marks omitted). Where, instead, the sentencing judge varies from the Guidelines “based solely on the judge’s view that the Guidelines range fails properly to reflect § 3553(a) considerations even in a mine-run case,” the Supreme Court has suggested that “closer review may be in order.” Id. at 575 (internal quotation marks omitted). Nevertheless, in Kimbrough itself, the Supreme Court found that no “closer review” was warranted where a district court based its sentence on a policy disagreement with the 100-to-l crack cocaine vs. powder cocaine weight ratio, because the crack cocaine Guidelines are not based on empirical data and national experience, and hence “do not exemplify the Commission’s exercise of its characteristic institutional role.” Id.
We do not, however, take the Supreme Court’s comments concerning the scope and nature of “closer review” to be the last word on these questions. More will have to be fleshed out as issues present themselves. For instance, we note that some Guidelines enhancements and reductions apply without modulation to a wide range of conduct. The Armed Career Criminal Guidelines, to take one example, sharply increase the recommended sentences for firearms offenses where the defendant has a prior conviction for a “crime of violence.” U.S.S.G. § 2K2.1(a). The Guidelines’ definition of the term “crime of violence,” however, includes a wide spectrum of offenses of varying levels of seriousness, from, on the one hand, murder or rape, to, on the other hand, attempted burglary of a dwelling. Id. § 4B1.2(a)(2). Similarly, many Guidelines such as those covering “offenses involving taxation,” U.S.S.G. § 2T4.1, “antitrust offenses,” see id. § 2R1.1, and larceny, embezzlement, fraud, and similar crimes, see id. § 2B1.1, drastically vary as to the recommended sentence based simply on the amount of money involved.10 Here again a district court may find that even after giving weight to the large or small financial impact, there is a wide variety of culpability amongst defendants and, as a result, impose different sentences based on the factors identified in § 3553(a). Cf. United States v. Ebbers, 458 F.3d 110, 129 (2d Cir.2006) (concluding that the sentencing disparity between co-defendants in a securities fraud case was reasonable in light of the “varying degrees of culpability and cooperation between the various defendants”). Such district court decisions, if adequately explained, should be reviewed especially deferentially.
But what does the procedural requirement, that the district court must explain its reasons for its chosen sentence, entail? The statutory scheme has long required sentencing judges, “at the time of sentencing,” to state them reasons for imposing the particular sentence “in open court.” 18 U.S.C. § 3553(c). And where a non-[193] Guidelines sentence is selected, the district court must also explain its reasons for doing so “with specificity in the written order of judgment and commitment.” Id. § 3553(c)(2). Now that the Guidelines are advisory, and the sentencing decision is discretionary, the need for explanation has itself been modified.
Requiring judges to articulate their reasons serves several goals. Most obviously, the requirement helps to ensure that district courts actually consider the statutory factors and reach reasoned decisions. The reason-giving requirement, in addition, helps to promote the perception of fair sentencing. See Rita, 127 S.Ct. at 2468 (“Confidence in a judge’s use of reason underlies the public’s trust in the judicial institution. A public statement of those reasons helps provide the public with the assurance that creates that trust.”). Furthermore, the practice of providing reasons “helps [the sentencing process] evolve” by informing the ongoing work of the Sentencing Commission. Id. at 2469. Finally, for our own purposes, an adequate explanation is a precondition for “meaningful appellate review.” Gall, 128 S.Ct. at 597. We cannot uphold a discretionary decision unless we have confidence that the district court exercised its discretion and did so on the basis of reasons that survive our limited review. Without a sufficient explanation of how the court below reached the result it did, appellate review of the reasonableness of that judgment may well be impossible.
As a result, in its explanation the district court must satisfy us that it has “considered the parties’ arguments” and that it has a “reasoned basis for exercising [its] own legal decisionmaking authority.” Rita, 127 S.Ct. at 2468. But, what is adequate to fulfill these purposes necessarily depends on the circumstances. As we have often said, we do not require “robotic incantations” that the district court has considered each of the § 3553(a) factors. Crosby, 397 F.3d at 113 (quotation marks omitted); see also Fernandez, 443 F.3d at 30 (noting that “we presume, in the absence of record evidence suggesting otherwise, that a sentencing judge has faithfully discharged her duty to consider the statutory factors”). Sentencing is a responsibility heavy enough without our adding formulaic or ritualized burdens. And, a brief statement of reasons will generally suffice where the parties have addressed only “straightforward, conceptually simple arguments” to the sentencing judge. Rita, 127 S.Ct. at 2468. A district judge imposing a non-Guidelines sentence, however, should say why she is doing so, bearing in mind, once again, that “a major departure [from the Guidelines] should be supported by a more significant justification than a minor one,” Gall, 128 S.Ct. at 597, and that varying from the Guidelines in a “mine-run” case may invite closer appellate review, especially when the Guidelines at issue are a product of traditional empirical and experiential study, Kimbrough, 128 S.Ct. at 575.
When all is said and done though, once we are sure that the sentence resulted from the reasoned exercise of discretion, we must defer heavily to the expertise of district judges. This circumspect form of review, it is true, may result in substantial variation among district courts. But “some departures from uniformity [are] a necessary cost” of the Booker remedy. Id. at 574. And in its recent cases, the Supreme Court has made clear its view that disparities in sentences imposed by different district judges are more likely to reflect justified differences than are those arising from differences of opinion among appellate panels. This last point may not be easy for appellate panels to accept, but [194] we believe that it is what the Supreme Court has instructed.
In this respect, we emphasize that sentencing discretion is like an elevator in that it must run in both directions. Under Gall, Kimbrough, and Irizarry v. United States, — U.S.-, 128 S.Ct. 2198, 171 L.Ed.2d 28 (2008), district courts have the power to impose sentences both above and below the Guidelines range. See Irizarry, 128 S.Ct. at 2204 (upholding a district court’s imposition of an above-Guideline sentence); Gall, 128 S.Ct. at 600-02 (upholding a district court’s decision to impose a non-custodial sentence where the Guidelines recommended at least thirty months in prison); Kimbrough, 128 S.Ct. at 576 (upholding a district court’s decision to impose a sentence four-and-a-half years lower than the bottom end of the Guidelines range, where the district court found that the crack cocaine Guidelines overstated the need to punish the defendant).
B.
How do these considerations apply in the case before us? We begin by asking whether the court below committed any “significant procedural error.” Gall, 128 S.Ct. at 597. We find no error in the district court’s calculation of the Guidelines range.11 Judge Sifton, moreover, clearly considered the Guidelines, and certainly did not treat that range as mandatory nor presume that it was reasonable.
Cavera contends that the district court erred proeedurally by failing to give him an adequate advance explanation of the court’s intent to impose an above-Guidelines sentence. Under Federal Rules of Criminal Procedure 32(h) and 32(i)(l)(C), it appears that a district court must provide a defendant with notice of its intent to impose a non-Guidelines sentence and an opportunity to challenge the grounds for such a sentence. The Supreme Court recently held, however, that any “expectation subject to due process protection ... that a criminal defendant would receive a sentence within the presumptively applicable guideline range did not survive ... United States v. Booker.” Irizarry, 128 S.Ct. at 2202. Consequently, this requirement of reasonable notice no longer applies to sentences at variance with the Guidelines’ recommended range. Nonetheless, “[s]ound practice dictates that judges in all cases should make sure that the information provided to the parties in advance of the hearing, and in the hearing itself, has given them an adequate opportunity to confront and debate the relevant issues.” Id. at 2203. We conclude that Judge Sifton followed this sound practice. He did so by informing the parties that he was considering an above-Guidelines sentence because the crime involved trafficking guns to New York City, by referring the parties to relevant articles on the subject, and by adjourning the proceedings so that the parties could prepare submissions and make arguments on the question of whether local variation was justified.
Whether or not the district court’s decision in this case reflected a categorical policy disagreement with the Guidelines,12 the Supreme Court’s recent teachings [195] strongly suggest that such a disagreement does not suffice to render that decision either procedurally or substantively unreasonable. It is now clear that, in appropriate circumstances, district courts may rely on categorical factors to increase or decrease sentences. There is, in addition, no special reason to think that reliance on a locality-based categorical factor is — without more — suspect. The environment in which a crime was perpetrated may, in principle, inform a district court’s judgment as to the appropriate punishment in any number of ways. We agree with Judge Sifton that, while a district court should not rely on “subjective considerations such as ‘local mores’ or feelings about a particular type of crime,” a finding “that the crime will have a greater or lesser impact given the locality of its commission is appropriately considered in crafting a reasonable sentence post-Booker.” Lucania, 379 F.Supp.2d at 296. As always, the more specifically in the purposes of sentencing a district court’s rationale is grounded, the more likely it is to survive appellate inspection. Cf. United States v. Politano, 522 F.3d 69, 72 (1st Cir.2008) (affirming an above-Guidelines sentence for a gun trafficking offense where the district court made a specific finding that there was an “ ‘epidemic of handgun violence in communities within [the District of Massachusetts]’ ”).
Judge Sifton stated expressly that he did not base his decision on “local feelings” in New York that gun trafficking is more serious. Lucania, 379 F.Supp.2d at 294. The district court can properly be read to have rested its decision that a sentence above the Guidelines range was necessary to satisfy the § 3553(a)(2) factors on two independent grounds. The first ground was the nonspecific geographical and demographic fact that New York City is a large metropolitan area. In this respect, Judge Sifton observed that urban areas have higher homicide rates than suburban and rural areas; that in those parts of New York City included in the Eastern District of New York, population density sometimes exceeded 35,000 persons per square mile when the national average was only 78 persons per square mile; and that guns smuggled into New York City frequently end up in the hands of persons not legally authorized to possess them and are used for illegitimate purposes. Id. at 295. From these circumstances, he concluded that firearm trafficking into New York City, and specifically into those boroughs in the Eastern District of New York, presented a greater risk of harm. The district court’s second ground focused instead on New York’s stricter gun regulatory scheme. More stringent local regulation in New York, the district court found, “renders gun running a more serious problem and creates a larger [and more profitable] black market” than in other places. Id. Accordingly, on the district court’s view, “a more severe penalty is necessary to produce adequate deterrence.” Id.
As to the district court’s first ground, our Court is divided. Were it necessary to reach the issue, some of us would hold that the district court, in its wide discretion, permissibly relied on a determination that trafficking guns into an urban area is likely to create more harm than the national average offense envisaged by the Guidelines. Others would hold that the district court erred to the extent that it based the sentence on the notion that guns are more dangerous in metropolitan areas. Still others are unsure whether reference to such broad, nonspecific geographical and demographic factors is appropriate in the context of this case.
We need not resolve that disagreement today, because the district court’s second ground, that of deterrence, [196] provides an independently sufficient justification for its variation from the Guidelines.13 The court clearly concluded that the existence and enforcement of strict local gun laws in a particular jurisdiction is likely to make the cost of getting a gun in that jurisdiction higher than in a jurisdiction with lax anti-gun laws. This, the court indicated, will increase the profits to be had from trafficking guns into the strong-enforcement jurisdiction. There is considerable support for this opinion. See Philip J. Cook et al., Guns and Violence Symposium: Regulating Gun Markets, 86 J.Crim. L. & Criminology 59, 72 (1995) (“In cities such as New York and Boston, where the prevalence of gun ownership is low because legal transactions are subject to onerous regulations or are banned, prices in the secondary market are higher than in other east coast locales.... As a result, dealers have long been able to make a profit by buying guns in Virginia or points south and running them northward to the street markets of northeastern cities.”); Gary Kleck, BATF Gun Trace Data and the Role of Organized Gun Traf-ficlcing in Supplying Guns to Criminals, 18 St. Louis U. Pub.L.Rev. 23, 28-29 (1999) (explaining that in cities subject to “unusually strict gun laws ... opportunities for gun traffickers to profit should be at their maximum”).14 Where the profits to be made from violating a law are higher, the penalty needs to be correspondingly higher to achieve the same amount of deterrence. See Richard A. Posner, Economic Analysis of the Law, § 7.2 (3d ed. 1986) (“A person commits a crime because the expected benefits of the crime to him exceed the expected costs.”).
Like any economic theory, these points are not uncontroversial, but it is not an abuse of discretion for courts to rely on this form of reasoning in deciding on an appropriate sentence. Indeed, the statutory requirement that sentencing courts consider, on a case by case basis, what is necessary for “deterrence to criminal conduct,” 18 U.S.C. § 3553(a)(2)(B), almost inevitably makes judges focus on notions and theories that may be controversial to some.15
[197] Of course, Cavera was selling guns in Florida, not in New York. The evidence, however, supported an inference that Cav-era knew the guns he sold were destined for New York. Although he was not himself the exporter to New York, he was a knowing participant in the traffic heading in that direction. As a result, there was no abuse of discretion in the court’s decision to consider New York market conditions in order to accomplish the goal of general deterrence.
In the course of an unusually detailed explanation of his reasoning, Judge Sifton discussed the relevant § 3553(a) considerations, and explained with particularity his basis for disagreeing with the Guidelines recommendation in the specific context of Cavera’s case. Judge Sifton, moreover, reached an individualized judgment as to what the purposes of sentencing required in this case. In view of Cavera’s advanced age, the district court chose to reduce the sentence it would otherwise have imposed based on its perception that Cavera was less likely than the average offender to reoffend. In addition, Judge Sifton explicitly considered the need to avoid unwarranted sentence disparities, and concluded that sentencing disparities among different federal districts were warranted by, among other things, the greater need for deterrence in New York, with its more profitable black market in firearms. Given the deference we owe to district judges, especially after Gall and Kimbrough, this deterrence-based rationale easily suffices to justify the sentence. It follows that it would not be an abuse of discretion to impose a prison sentence of twenty-four months that exceeded the top end of the Guideline range by just six months, and a fine that surpassed the Guidelines maximum by $30,000. In relation to both the recommended Guidelines sentence and the § 3553(a) factors, the sentence is substantively reasonable.
What then of the broad demographic and geographic factors the district court considered? It seems clear to us from the record that the district court would have imposed the same sentence had it relied solely on the New York-specific rationale that the local gun regulatory scheme created a heightened need for deterrence in this case. In these circumstances, we need not decide whether the district court erred when it also relied, in the alternative, on the wider notions of geographic and demographic variation because, even if we were to identify error, it would be harmless in the light of the alternative independent ground for the challenged sentence. Since any such error would be harmless, the sentence imposed in this case withstands appellate review.
III.
The panel decision is VACATED, and the judgment of the district court is AFFIRMED.