Transcontinental Gas Pipe Line Corp. v. State Oil & Gas Board

*411Justice Blackmun

delivered the opinion of the Court.

We are confronted again with the issue of a state regulation requiring an interstate pipeline to purchase gas from all the parties owning interests in a common gas pool. The purchases would be in proportion to the owners’ respective interests in the pool, and would be compelled even though the pipeline has pre-existing contracts with less than all of the pool’s owners.

This Court, in Northern Natural Gas Co. v. State Corporation Comm’n of Kansas, 372 U. S. 84 (1963), struck down, on pre-emption grounds, a virtually identical regulation. In the present case, however, the Supreme Court of Mississippi ruled that the subsequently enacted Natural Gas Policy Act of 1978 (NGPA), 92 Stat. 3351, 15 U. S. C. §3301 et seq., effectively nullified Northern Natural by vesting regulatory power in the States over the wellhead sale of gas. The Mississippi Supreme Court went on to hold that the Mississippi regulation did not impermissibly burden interstate commerce. Because of the importance of the issues in the functioning of the interstate market in natural gas, we noted probable jurisdiction. 470 U. S. 1083 (1985).

I

The Harper Sand gas pool lies in Marion County in southern Mississippi. Harper gas is classified as “high-cost natural gas” under NGPA’s § 107(c)(1), 15 U. S. C. § 3317(c)(1), because it is taken from a depth of more than 15,000 feet. At the time of the proceedings before appellee State Oil and Gas Board of Mississippi, six separate wells drew gas from the pool. A recognized property of a common pool is that, as gas is drawn up through one well, the pressure surrounding *412that well is reduced and other gas flows towards the area of the producing well. Thus, one well can drain an entire pool, even if the gas in the pool is owned by several different owners. The interests of these other owners often are referred to as “correlative rights.” See, e. g., Miss. Code Ann. § 53-1-1 (1972 and Supp. 1985).

Some owners of interests in the Harper Sand pool, such as appellee Getty Oil Co., actually drill and operate gas wells. Others, such as appellee Coastal Exploration, Inc., own smaller working interests in various wells. Normally, these lesser owners rely on the well operators to arrange the sales of their shares of the production, see App. 26, although some nonoperator owners contract directly either with the pipeline that purchases the operator’s gas or with other customers.

Appellant Transcontinental Gas Pipe Line Corporation (Transco) operates a natural gas pipeline that transports gas from fields in Texas, Louisiana, and Mississippi for resale to customers throughout the Northeast. Beginning in 1978, Transco entered into 35 long-term contracts with Getty and two other operators, Florida Exploration Co. and Tomlinson Interests, Inc., to purchase gas produced from the Harper Sand pool. In line with prevailing industry practice, the contracts contained “take-or-pay” provisions. These essentially required Transco either to accept currently a certain percentage of the gas each well was capable of producing, or to pay the contract price for that gas with a right to take delivery at some later time, usually limited in duration. Take-or-pay provisions enable sellers to avoid fluctuations in cash flow and are therefore thought to encourage investments in well development. See Pierce, Natural Gas Regulation, Deregulation, and Contracts, 68 Va. L. Rev. 63, 77-79 (1982).

Transco entered into these contracts during a period of national gas shortage. Transco’s contracts with Getty and Tomlinson obligated it to buy only Getty’s and Tomlinson’s own shares of the gas produced by the wells they operated, *413while its contracts with Florida Exploration required it to take virtually all the gas Florida Exploration’s wells produced, regardless of its ownership. See App. 107. But demand was sufficiently high that Transco also purchased, on a noncontract basis, the production shares of smaller owners, such as Coastal, in the Getty and Tomlinson wells. Id., at 155. In the spring of 1982, however, consumer demand for gas dropped significantly, and Transco began to have difficulty selling its gas. It therefore announced in May 1982 that it would no longer purchase gas from owners with whom it had not actually contracted. See, e. g., id., at 41-42. Transco refused Coastal’s request that it be allowed to ratify Getty’s contract, and made a counteroffer, which Coastal refused, either to purchase Coastal’s gas at a significantly lower price than it was obligated to pay under its existing contracts or to transport Coastal’s gas to other customers if Coastal arranged such sales. See id., at 66-69. Fifty-five other noncontract owners of Harper gas, however, did accept such offers from Transco. See 457 So. 2d 1298, 1309 (Miss. 1984).

Getty and Tomlinson cut back production so that their wells produced only that amount of gas equal to their ownership interests in the maximum flow. The immediate economic effect of the cutback was to deprive Coastal of revenue, because none of its share of the Harper gas was being produced. The ultimate geological effect, however, is that gas will flow from the Getty-Tomlinson areas of the field, which are producing at less than capacity, to the Florida Exploration areas; gas owned by interests that produce through Getty’s and Tomlinson’s wells thus may be siphoned away. Moreover, because of the decrease in pressure, gas left in the ground, such as Coastal’s gas, may become more costly to recover and therefore its value at the wellhead may decline.

*414I — I h — I

On July 29, 1982, Coastal filed a petition with appellee State Oil and Gas Board of Mississippi, asking the Board to enforce its Statewide Rule 48, a “ratable-take” requirement. Rule 48 provides:

“Each person now or hereafter engaged in the business of purchasing oil or gas from owners, operators, or producers shall purchase without discrimination in favor of one owner, operator, or producer against another in the same common source of supply.”

Rule 48 never before had been employed to require a pipeline actually to purchase noncontract gas; rather, its sole purpose appears to have been to prevent drainage, that is, to prevent a buyer from contracting with one seller and then draining a common pool of all its gas. See 457 So. 2d, at 1306. The Gas Board conducted a 3-day evidentiary proceeding. It found Transco in violation of Rule 48, and, by its Order No. 409-82, filed Oct. 13, 1982,1 ordered Transco to start taking gas “ratably” (i. e., in proportion to the various owners’ shares) from the Harper Sand pool, and to purchase the gas under nondiscriminatory price and take-or-pay conditions.

Transco appealed the Gas Board’s ruling to the Circuit Court of the First Judicial District of Hinds County, Miss. In the parts of its opinion relevant to this appeal, the Circuit Court held that the Gas Board’s authority was not pre*415empted by either the Natural Gas Act of 1938 (NGA), eh. 556, 52 Stat. 821, 15 U. S. C. §717 et seq., or the NGPA; that the NGPA effectively overruled Northern Natural; and that the Gas Board’s order did not run afoul of the Commerce Clause of the United States Constitution.

The Mississippi Supreme Court affirmed that portion of the Circuit Court’s judgment. 457 So. 2d 1298 (1984). With respect to Transco’s pre-emption claim, the court recognized that, prior to 1978, the Federal Energy Regulatory Commission (FERC) and its predecessor, the Federal Power Commission, possessed “plenary authority to regulate the sale and transportation of natural gas in interstate commerce.” Id., at 1314. Under the interpretation of that authority in Northern Natural, where a Kansas ratable-take order was ruled invalid because the order “invade[d] the exclusive jurisdiction which the Natural Gas Act has conferred upon the Federal Power Commission,” 372 U. S., at 89, Mississippi’s “authority to enforce Rule 48 requiring ratable taking had been effectively suspended — preempted, if you will, and any orders such as Order No. 409-82 would have been wholly unenforceable.” 457 So. 2d, at 1314. But the court went on to conclude that the enactment of the NGPA in 1978 removed FERC’s jurisdiction over “high-cost” gas (the type produced from the Harper Sand pool). Under § 601(a)(1) of the NGPA, “the Natural Gas Act of 1938 (NGA) and FERC’s jurisdiction under the Act never apply to deregulated gas” (emphasis added), 457 So. 2d, at 1316, and “[t]hat message is decisive of the preemption issue in this case.” Ibid.

The court also found no implicit pre-emption of Rule 48. Transco’s compliance with the Rule could not bring it into conflict with any of FERC’s still-existing powers over the gas industry. The court noted that, under Arkansas Electric Cooperative Corp. v. Arkansas Public Service Comm’n, 461 U. S. 375, 384 (1983), a federal determination that deregulation was appropriate was entitled to as much weight in determining pre-emption as a federal decision to regulate actively. *416Although the NGPA stemmed from Congress’ desire to deregulate the gas industry, the court found that “[hjowever consistent a continued proscription on state regulation might have been with the theoretical underpinnings of deregulation, the Congress in NGPA in 1978 did not ban state regulation of deregulated gas.” 457 So. 2d, at 1318.

In addressing the Commerce Clause issue, the court relied on the balancing test set out in Pike v. Bruce Church, Inc., 397 U. S. 137 (1970): when a state law “regulates evenhandedly to effectuate a legitimate local public interest, and its effects on interstate commerce are only incidental, it will be upheld unless the burden imposed on such commerce is clearly excessive in relation to the putative local benefits.” Id., at 142. In weighing the benefit against the burden, a reviewing court should consider whether the local interest “could be promoted as well with a lesser impact on interstate activities.” Ibid. The court found that Rule 48 had a legitimate local purpose — the prevention of unfair drainage from commonly owned gas pools. It identified the principal burden on interstate commerce as higher prices for the ultimate consumers of natural gas. But, under Cities Service Gas Co. v. Peerless Oil & Gas Co., 340 U. S. 179, 186-187 (1950), higher prices do not render a state regulation impermissible per se under the Commerce Clause. Also, Congress expressed a clear intent in enacting the NGPA that “all reasonable costs of production of natural gas shall be borne ultimately by the consumer. . . . Congress within the scope of its power under the affirmative Commerce Clause has expressly authorized such increases.” 457 So. 2d, at 1321. Transco had identified one other potential burden on interstate commerce: Rule 48 would require it to take more gas from Mississippi’s fields than would otherwise be the case, thereby leading Transco to reduce its purchases from Louisiana and Texas. But the Mississippi court rejected this argument, noting both that Texas and Louisiana had their own ratable-take regulations, which presumably would protect *417their producers, and that the actual cause of any such effect was Transco’s imprudent entry into take-or-pay contracts, rather than the State’s ratable-take requirement. Transco knew of Rule 48’s existence when it entered into its various contracts and should have foreseen the risk that it would be required to purchase smaller owners’ shares. Moreover, since Transco was permitted to pass along its increased costs, the consumer ultimately would bear this burden, which was “simply one inevitable consequence of the free market policies of the era of deregulation with respect to which Transco is vested by the negative Commerce Clause with no right to complain.” Id., at 1322.

Finally, the court rejected Transco’s argument that the State could have served the same local public interest through a ratable-production order rather than through a ratable-take order. It held that it need not even consider whether less burdensome alternatives to the ratable-take order existed, because Transco had failed to meet the threshold requirement of demonstrating an unreasonable burden on interstate commerce.2

Ill

If the Gas Board’s action were analyzed under the standard used in Northern Natural, it clearly would be pre-empted. Whether that decision governs this case depends on whether Congress, in enacting the NGPA, altered those characteristics of the federal regulatory scheme which provided the basis in Northern Natural for a finding of pre-emption.

*418In that case this Court considered whether the “comprehensive scheme of federal regulation” that Congress enacted in the NGA pre-empted a Kansas ratable-take order. 372 U. S., at 91. • Northern Natural Gas Company had a take-or-pay contract with Republic Natural Gas Company to purchase all the gas Republic could produce from its wells in the Hugoton Field. Northern also had contracts with other producers to buy their production, but those contracts required it to purchase their gas only to the extent that its requirements could not be satisfied by Republic. Id., at 87. Northern historically had taken ratably from all Hugoton wells, but, starting in 1958, it no longer needed all the gas the wells in the field were capable of producing. It therefore reduced its purchases from the other wells, causing drainage toward Republic’s wells. The Kansas Corporation Commission, which previously had imposed a ratable-production order on the Hugoton producers,3 then issued a ratable-take order requiring Northern to “take gas from Republic wells in no higher proportion to the allowables than from the wells of the other producers.” Id., at 88.

Kansas argued that its order represented a permissible attempt to protect the correlative rights of the other producers. The Court rejected this contention. Section 1(b) of the NGA, 15 U. S. C. § 717(b), provided that the Act’s provisions “shall not apply ... to the production or gathering of natural gas.” But the Court, it was said, “has consistently held that ‘production’ and ‘gathering’ are terms narrowly confined to the physical acts of drawing the gas from the earth and preparing it for the first stages of distribution.” 372 U. S., at 90. Since Kansas’ order was directed not at “a producer but *419a purchaser of gas from producers,” ibid., Northern, being a purchaser, was not expressly exempted from the Act’s coverage.

Although it was “undeniable that a state may adopt reasonable regulations to prevent economic and physical waste of natural gas,” Cities Service Gas Co. v. Peerless Oil & Gas Co., 340 U. S., at 185, the Court did not view the ratable-take rule as a permissible conservation measure.4 Such measures target producers and production, while ratable-take requirements are “aimed directly at interstate purchasers and wholesales for resale.” Northern Natural, 372 U. S., at 94.

The Court identified the conflict between Kansas’ rule and the federal regulatory scheme in these terms: Congress had “enacted a comprehensive scheme of federal regulation of ‘all wholesales of natural gas in interstate commerce.’” Id., at 91, quoting Phillips Petroleum Co. v. Wisconsin, 347 U. S. 672, 682 (1954). “[UJniformity of regulation” was one of its objectives. 372 U. S., at 91-92. And, it was said:

“The danger of interference with the federal regulatory scheme arises because these orders are unmistakably and unambiguously directed at purchasers who take gas in Kansas for resale after transportation in interstate commerce. In effect, these orders shift to the shoulders of interstate purchasers the burden of performing the complex task of balancing the output of thousands of natural gas wells within the State .... Moreover, any readjustment of purchasing patterns which such orders *420might require of purchasers who previously took un-ratably could seriously impair the Federal Commission’s authority to regulate the intricate relationship between the purchasers’ cost structures and eventual costs to wholesale customers who sell to consumers in other States” (emphasis in original). Id., at 92.

Northern Natural’s finding of pre-emption thus rests on two considerations. First, Congress had created a comprehensive regulatory scheme, and ratable-take orders fell within the limits of that scheme rather than within the category of regulatory questions reserved for the States. Second, in the absence of ratable-take requirements, purchasers would choose a different, and presumably less costly, purchasing pattern. By requiring pipelines to follow the more costly pattern, Kansas’ order conflicted with the federal interest in protecting consumers by ensuring low prices.

Under the NGA, the Federal Power Commission’s comprehensive regulatory scheme involved “utility-type rate-making” control over prices and supplies. See Haase, The Federal Role in Implementing the Natural Gas Policy Act of 1978, 16 Houston L. Rev. 1067, 1079 (1979). The FPC set price ceilings for sales from producers to pipelines and regulated the prices pipelines could charge their downstream customers. But “[i]n the early 1970’s, it became apparent that the regulatory structure was not working.” Public Service Comm’n of New York v. Mid-Louisiana Gas Co., 463 U. S. 319, 330 (1983). The Nation began to experience serious gas shortages. The NGA’s “artificial pricing scheme” was said to be a “major cause” of the imbalance between supply and demand. See S. Rep. No. 95-436, p. 50 (1977) (additional views of Senators Hansen, Hatfield, McClure, Bartlett, Weicker, Domenici, and Laxalt).

In response, Congress enacted the NGPA, which “has been justly described as ‘a comprehensive statute to govern future natural gas regulation.’” Mid-Louisiana Gas. Co., 463 U. S., at 332, quoting Note, Legislative History of the Natu*421ral Gas Policy Act, 59 Texas L. Rev. 101, 116 (1980). The aim of federal regulation remains to assure adequate supplies of natural gas at fair prices, but the NGPA reflects a congressional belief that a new system of natural gas pricing was needed to balance supply and demand. See S. Rep. No. 95-436, at 10. The new federal role is to “overse[e] a national market price regulatory scheme.” Haase, 16 Houston L. Rev., at 1079; see S. Rep. No. 95-436, at 21 (NGPA implements “a new commodity value pricing approach”). The NGPA therefore does not constitute a federal retreat from a comprehensive gas policy. Indeed, the NGPA in some respects expanded federal control, since it granted FERC jurisdiction over the intrastate market for the first time. See the Act’s §§311 and 312, 15 U. S. C. §§3371 and 3372.

Appellees argue, however, that §§601(a)(l)(B)(i) and (ii), 15 U. S. C. §§3431(a)(l)(B)(i) and (ii), stripped FERC of jurisdiction over the Harper Sand pool gas which was the subject of the Gas Board’s Rule 48 order, thereby leaving the State free to regulate Transco’s purchases. Section 601(a)(1)(B) states that “the provisions of [the NGA] and the jurisdiction of the Commission under such Act shall not apply solely by reason of any first sale” of high-cost or new natural gas. Moreover, although FERC retains some control over pipelines’ downstream pricing practices, § 601(c)(2) requires FERC to permit Transco to pass along to its customers the cost of the gas it purchases “except to the extent the Commission determines that the amount paid was excessive due to fraud, abuse, or similar grounds.” According to appel-lees, FERC’s regulation of Transco’s involvement with high-cost gas can now concern itself only with Transco’s sales to its customers; FERC, it is said, cannot interfere with Transco’s purchases of new natural gas from its suppliers. Appellees believe that the Gas Board order concerns only this latter relationship, and therefore is not pre-empted by federal regulation of other aspects of the gas industry.

*422That FERC can no longer step in to regulate directly the prices at which pipelines purchase high-cost gas, however, has little to do with whether state regulations that affect a pipeline’s costs and purchasing patterns impermissibly intrude upon federal concerns. Mississippi’s action directly undermines Congress’ determination that the supply, the demand, and the price of high-cost gas be determined by market forces. To the extent that Congress denied FERC the power to regulate affirmatively particular aspects of the first sale of gas, it did so because it wanted to leave determination of supply and first-sale price to the market. “[A] federal decision to forgo regulation in a given area may imply an authoritative federal determination that the area is best left -unregulated, and in that event would have as much preemptive force as a decision to regulate” (emphasis in original). Arkansas Electric Cooperative Corp. v. Arkansas Public Service Comm’n, 461 U. S., at 384. Cf. Machinists v. Wisconsin Employment Relations Comm’n, 427 U. S. 132, 150-151 (1976).

The proper question in this case is not whether FERC has affirmative regulatory power over wellhead sales of § 107 gas, but whether Congress, in revising a comprehensive federal regulatory scheme to give market forces a more significant role in determining the supply, the demand, and the price of natural gas, intended to give the States the power it had denied FERC. The answer to the latter question must be in the negative. First, when Congress meant to vest additional regulatory authority in the States it did so explicitly. See §§ 503(c) and 602(a), 15 U. S. C. §§3413(c) and 3432(a). Second, although FERC may now possess less regulatory jurisdiction over the “intricate relationship between the purchasers’ cost structures and eventual costs to wholesale customers who sell to consumers in other States,” Northern Natural, 372 U. S., at 92, than it did under the old regime, that relationship is still a subject of deep federal concern. FERC still must review Transco’s pricing practices, even *423though its review of Transco’s purchasing behavior has been circumscribed. See App. 148-150, 170. In light of Congress’ intent to move toward a less regulated national natural gas market, its decision to remove jurisdiction from FERC cannot be interpreted as an invitation to the States to impose additional regulations.

Mississippi’s order also runs afoul of other concerns identified in Northern Natural. First, it disturbs the uniformity of the federal scheme, since interstate pipelines will be forced to comply with varied state regulations of their purchasing practices. In light of the NGPA’s unification of the interstate and intrastate markets, the contention that Congress meant to permit the States to impose inconsistent regulations is especially unavailing. Second, Mississippi’s order would have the effect of increasing the ultimate price to consumers. Take-or-pay provisions are standard industrywide. See Pierce, 68 Va. L. Rev., at 77-78; H. R. Rep. No. 98-814, pp. 23-25, 133-134 (1984). Pipelines are already committed to purchase gas in excess of market demand. Mississippi’s rule will require Transco to take delivery of noncontract gas; this will lead Transco not to take delivery of contract gas elsewhere, thus triggering take-or-pay provisions. Trans-co’s customers will ultimately bear such increased costs, see App. 161, unless FERC finds that Transco’s purchasing practices are abusive. In fact, FERC is challenging, on grounds of abuse, the automatic passthrough of some of the costs Transco has incurred in its purchases of high-cost gas. See App. 177-178.5 In any event, the federal scheme is dis*424rupted: if customers are forced to pay higher prices because of Mississippi’s ratable-take requirement, then Mississippi’s rule frustrates the federal goal of ensuring low prices most effectively; if FERC ultimately finds Transco’s practices abusive and refuses to allow a passthrough, then FERC’s and Mississippi’s orders to Transco will be in direct conflict.

The change in regulatory perspective embodied in the NGPA rested in significant part on the belief that direct federal price control exacerbated supply and demand problems by preventing the market from making long-term adjustments.6 Mississippi’s actions threaten to distort the market once again by artificially increasing supply and price. Although, in the long run, producers and pipelines may be able to adjust their selling and purchasing patterns to take account of ratable-take orders, requiring such future adjustments in an industry where long-term contracts are the norm *425will postpone achievement of Congress’ aims in enacting the NGPA. We therefore conclude that Mississippi’s ratable-take order is pre-empted.

IV

Because we have concluded that the Gas Board’s order is pre-empted by the NGA and NGPA, we need not reach the question whether, absent federal occupation of the field, Mississippi’s action would nevertheless run afoul of the Commerce Clause.

The judgment of the Supreme Court of Mississippi is therefore reversed.

It is so ordered.

Order No. 409-82 directed Transco “forthwith to comply with Statewide Rule 48 of the State Oil and Gas Board of Mississippi in its purchases of gas from the said Harper Sand Gas Pool in Greens Creek and East Mor-gantown Fields, and. . . ratably take and purchase gas without discrimination in favor of one owner, operator or producer against another in the said common source of [sic] pool; and, specifically, in the event it so chooses and elects to take and purchase gas produced from the said common pool, Transco shall ratably take and purchase without discrimination in favor of the operators Getty and Tomlinson against Coastal, the Fairchilds, and Inexco.” App. to Pet. for Cert. 112a.

Transco’s other claims, a void-for-vagueness challenge, a Takings Clause argument, and various state-law claims, were rejected with one exception. The court found that, although the Gas Board had the power to order Transco to take ratably from the Harper Sand pool, it lacked the power to prohibit Transco from paying different prices for gas owned by nonparties to its original contracts. Therefore, Transco need pay Coastal only the current market price, rather than the higher price it was paying Getty and Tomlinson under its contracts with them.

A ratable-production order in essence allocates pro rata among interest owners the right to produce the amount of gas demanded. For example, if one interest owner owns 75% of the gas in a common pool with 100 units of gas and demand is 60 units, then the majority owner will be permitted to sell only 45 of his units, even though he owns, and is capable of producing, 75 units.

The Court noted, 340 U. S., at 185, that it had “upheld numerous kinds of state legislation designed to curb waste of natural resources and to protect the correlative rights of owners through ratable taking, Champlin Refining Co. v. Corporation Commission of Oklahoma, 286 U. S. 210 (1932),” but it is clear from the context of that statement that those challenges had involved claims by gas owners under the Due Process and Equal Protection Clauses, rather than claims of federal pre-emption: “These ends have been held to justify control over production even though the uses to which property may profitably be put are restricted.” Id., at 185-186.

On October 31, 1985, FERC issued an initial decision, Transcontinental Gas Pipe Line Corp., 33 FERC ¶63,026, finding that Transeo’s purchases of Harper Sand gas pursuant to the ratable-take order were not imprudent. But the grounds on which the Administrative Law Judge rested his conclusion demonstrate how Mississippi’s action impermissibly interferes with FERC’s regulatory jurisdiction.

FERC’s staff had requested the judge to order Transco “to pursue a least-cost purchasing strategy irrespective of Rule k8. ” Id., at 65,073 (emphasis in original). The judge refused: “In my view, Transco is entitled, *424indeed is required, to follow the decisions of the Mississippi authorities until and unless they be overturned by the Supreme Court of the United States.” Id., at 65,074.

Had the judge considered FERC’s claim on the merits, the conflict between the federal and state schemes would be patent. But his belief that he was constrained to find Transco’s practices reasonable because they were undertaken in compliance with Mississippi law is almost as demonstrative of pre-emption. First, Mississippi cannot be permitted to foreclose what would otherwise be more searching federal oversight of purchasing practices. Second, the mere exercise of federal regulatory power, even if it does not result in invalidation of the challenged act, shows continued federal occupation of the field. Since no evidence exists to suggest Congress intended FERC’s power to be circumscribed by state action, Rule 48 is pre-empted.

The dissent’s complaint that Congress did not intend to decontrol supply and demand, post, at 433, n. 5, misses the point. Congress clearly intended to eliminate the distortive effects that NGA price control had had on supply and demand. To suggest that Congress was willing to replace this distortion with a distortion on price caused by a State’s decision to require pipelines and, ultimately, interstate consumers, to purchase gas they do not want — the purpose of the order in this case — requires taking an artificially formalistic view of what Congress sought to achieve in the NGPA.