The Staggers Rail Act of 1980, Pub.L.No. 96-4M8, 95 Stat. 1895 (to be codified in scattered sections of 11, 45 & 49 U.S.C.) (“Staggers Act” or “Act”) provides the Interstate Commerce Commission (“ICC” or “Commission”) with jurisdiction to review the reasonableness of rates charged by “market dominant”
I. BACKGROUND
A. Statutory Context
Under the Staggers Act, market dominance of a railroad in a particular market is determined by the ratio of rates to variable costs. If this “revenue-variable cost perсentage” exceeds a certain level, the Commission has jurisdiction to review the reasonableness of the rate charged. See 49 U.S.C.A. §§ 10701a(b)(1), 10709(d)(2) (West Supp.1981). This threshold test, set initially at 160% for the year ending September 30, 1981, will increase to 175% for the year ending September 30, 1984.
Rates that met this test of market dominance at the time of the Staggers Act’s enactment could have been challenged within 180 days of the passage of the Act. See 49 U.S.C.A. § 10701a note (West Supp. 1981). Rates determined in such a proceeding became “base rates” for the applicable service. Similarly, rates that were not challenged or were not initially subject to challenge also became base rates. Pursuant to section 203 of the Act, 49 U.S.C.A. § 10707a (West Supp.1981), these base rates are to be adjusted annually in accordance with an inflation cost index developed or verified by the Commission. The resulting “adjusted base rate” is not necessarily a rate that is actually charged by any railroad. Instead, it serves as a measuring stick by which the Commission considers the reasonableness of rate increases.
B. Adoption of the Modified AAR Index
The Commission’s sеarch for an index that would properly measure inflationary cost increases preceded the enactment of the Staggers Act. On April 22, 1980, the Commission issued an Advance Notice of Proposed Rulemaking in Ex Parte No. 290 (Sub. No. 2), Railroad Cost Recovery Procedures soliciting suggestions for measuring average cost increases for railroads. The Commission explained that it wished to establish a mechanism by which railroads could recover increased costs without being subjected to the length and uncertainty of individualized rate proceedings. See 45 Fed.Reg. 29,103-04 (1980); Joint Appendix (“J.A.”) 42—43. In response, the Commission received extensive comments from railroads, shippers, and purchasers of commodities shipped by rail. The railroads proposed that the Commission adopt the Association of American Railroad’s (“AAR”) index of rail costs. See Verified Statement of Dr. Paul O. Roberts & Dr. Brian C. Kullman, J.A. 52; Verified Statement of Dr. Harvey A. Levine, J.A. 420-24; Verified Statement of Mary Maher, J.A. 431—40. The shippers did not propose a specific cost index. They did suggest, however, that if the Commission adopted the AAR index it should adjust that index so that it would rеflect cost savings from productivity gains. See Verified Statement of Leroy E. Peabody, Jr., J.A. 389-400.
The AAR index is a classic Laspeyre’s price index,
At the heart of the shippers’ criticism of the AAR index was the difference between the prices railroads pay to purchase inputs (such as labor and materials) and the costs they incur in producing their output (rail service). The shippers argued that a proper measure of railroad “costs” must account for the possibility that productivity gains allow railroads to produce more rail service with the same “market basket” of railroad inputs. By accounting for these gains, they suggested that an input index (such as the AAR index) could and should be converted into an “output index” — namely an index of cost per unit of output.
Before the Commission completed its proceedings on inflationary rate adjustments,
Following further comments, the Commission issued a final rule adopting the modified AAR index as initially proposed. See
II. ANALYSIS
A. Consistency With the Staggers Act
The first question before us is whether the Commission properly interpreted its
[T]he Rail Act does not specify whether an input cost index or an output cost index is to be used as the rail cost adjustment factor. Instead, the Rail Act leaves this matter up to the Commission, as a matter of policy, to be determined in a manner consistent with the purpose of the Rail Act as a whole.
In their petitions for review, the Western Coal Traffic League (“WCTL”)
1. The “Plain Meaning” Debate
All sides of this controversy lay claim to the plain meaning of section 203. As we have often observed, the meaning of some statutory provisions is sufficiently clear to resolve disputes over their interpretation. See, e.g., McCord v. Bailey,
Section 203 requires that:
Commencing with the fourth quarter of 1980, the Commission shall, as often as practicable but in no event less often than quarterly, publish a rail cost adjustmentfactor which shall be a fraction, the numerator of which is the latest published Index of Railroad Costs (which index shall be compiled or verified by the Commission, with appropriate adjustments to reflect the changing composition of railroad costs, including the quality and mix of material and labor), and the denominator of which is the same index for the fourth quarter of 1980, or for the fourth quarter of 1982 or for the fourth quarter of every fifth year thereafter, as appropriate.
49 U.S.C.A. § 10707a(a)(2)(B) (West Supp. 1981) (emphasis added). CMA suggests that this language clearly indicates Congress’ concern with railroad costs. Thus, “the index must be adjusted to reflect cost changes due to changes in the mix of expenses incurred by railroads, including the use of less labor or fuel due to more efficient technology and operating methods.” CMA Brief 14. In short, an adequate measure of changing costs must account for more efficient uses of input items through productivity gains. The Commission’s attorneys, in an argument we find somewhat at odds with the Commission’s articulated position, contend that the common sense meaning of section 203 requires adoption of an input index. They state that “the natural, common sense meaning of the statutory phrase ‘composition of railroad costs’ is the formation of a total cost by putting together the different prices paid by railroads for the goods and services they purchase.” Government’s Brief 19. After noting that “the prices of labor and materials mentioned in the statute are indisputably inputs,” they state that: “Because none of the words in the statute embody concepts related to output, the statute cannot be read to embody productivity, which is a concept inextricably linked to output.” Government’s Brief 19.
We find neither interpretation of the “plain meaning” of section 203 very persuasive.
CMA’s “plain” reading is equally faulty. CMA asserts that a true cost index must include all factors bearing on cost per unit of output, even though the AAR index stands as a stark reminder that not all such indices make the fine adjustments it recommends. Furthermore, CMA overlooks the full statutory language of section 203, which only requires “appropriate” adjustments. Since one critical issue in this case is whether estimates of productivity gains on a quarterly basis are feasible, CMA’s contention that productivity is a cost factor, even if accepted, is insufficient to prove that a productivity adjustment is “appropriate” and, therefore, statutorily mandated.
2. Legislative History of Section 203
a. Redrafting of Section 203
As further support for their respective interpretations of section 203, the parties turn to the history of its revision in committee. The original version of S. 1946, the bill that became the Staggers Act, described the inflationary cost index as an “Index of Railroad Material Prices and Wages.” See S. 1946, 96th Cong., 2d Sess. § 103 (1980). This description clearly pointed towards an input index, if not the AAR index itself.
Section 203 attracted considerable attention during hearings on S. 1946. Numerous witnesses appearing before the Senate Committee on Commerce, Science, and Transportation argued that language describing an input index was inappropriate if the purpose of indexing base rates was simply to neutralize the effect of cost increases on railroad profits. These witnesses explained that the bill’s formula was “not flexible enough to recognize that certain carriers may come up with innovation, that change in volume, that change in traffic mix should be considered in the automatic adjustment.” See 1 Railroad Transportation Policy Act of 1979: Hearings on S. 1946 Before the Committеe on Commerce, Science and Transportation of the United States Senate, 96th Cong., 1st Sess. 395 (“Senate Hearings”) (statement of Edwin Wheeler).
These criticisms were repeated throughout the Senate hearings,
Senator Cannon: With regard to section [203], you note that the formula set forth in S.1946 doesn’t specifically require consideration of such factors as changes in traffic volume and labor productivity, although it does call for commission compilation or verification of any index.
Several witnesses have suggested that in compiling the index, specific consideration be given to changes in volume, productivity, and traffic mix.
I assume language along those lines, if adopted, would satisfy your concerns on that point.
Mr. Frost. I think it might very well satisfy my concerns.
As redrafted by the committeе, however, section 203 did not “specifically require consideration of such factors as changes in traffic volume and labor productivity.” Instead, it provided the Commission with a general mandate to make “appropriate adjustments to reflect the quality and mix of material and labor.” This language was modified once more in conference to require “appropriate adjustments to reflect the composition of costs, including the quality and mix of material and labor.”
Courts must exercise caution before drawing inferences regarding legislative intent from changes made in committee without explanation. See Trailmobile Co. v. Whirls,
b. Underlying Purpose of Section 203
The shippers ground their argument that section 203 mandates an output index on the purpose of the inflationary cost index. They contend that the underlying purpose of the inflationary cost index is to enable railroads to recover costs; no more and no less. Thus, they conclude, section 203 requires an output index, or at least an input index modified to approximate an output index. Otherwise, the index will authorize market dominant railroads to overrecover costs during periods of productivity growth at the expense of captive shippers.
We agree with the shippers that the principal function of the section 203 inflationary cost index is to provide a mechanism for recovering inflation-based costs, not to enhance revenues. But the legislative history of section 203 also demonstrates that Congress sought a cost-recovery mechanism that would avoid regulatory lag by operating with dispatch to assure that rates actually reflect current costs. Insofar as any particular methodology would interfere with achievement of this practical objective, its adoption cannot be characterized as mandated by the Act.
In introducing S.1946, Senator Cannon explained that the bill’s overall approach was “to provide the railroads with more pricing flexibility while protecting captive shippers” and to “streamlin[e] the administrative process” so as “to simplify rather than further complicate railroad regulation.” 125 Gong.Rec.S 15309 (daily ed. Oct. 29, 1979). To accomplish these purposes, S.1946 set up a simple test for determining whether a rate is subject to Commission review, and specified percentages by which railroads could increase rates without facing any threat of rate suspension. The bill, like the Act itself, set forth a two-part test for judging rate increases.
The railroad’s financial difficulties may be attributed in part to the timelag involved in recovering cost increases. This section will assure that rail rates reflect a carrier’s current costs.
125 Cong.Rec.S 15315 (daily ed. Oct. 29, 1979) (emphasis added). In contrast, he stated that the bill’s “rate flexibility zone above cost increases” within which shippers bear the burden of proving unreasonableness would “assist the railroads in achieving adequate revenue levels and [would] provide additional flexibility for rate changes without regulatory interference.” Id.
Throughout hearings on S.1946, witnesses adhered to the view that the function of the inflationary cost index was to allow railroads to receive rate increases warranted by cost increases without the expense and delay
Although witnesses at the Senate hearings рroposed changes in the bill’s language to assure that the index would accurately reflect incurred costs or to explicitly allow free rate increases above costs,
This consistent view of the function of the inflationary cost index, however, falls short of proving that section 203 envisions an output index. As the Commission noted, the theoretical validity of increasing rates in accordance with costs per unit of output is a different matter from the soundness of insisting that whatever “output” methodology is currently available be immediately incorporated into the cost index regardless of its reliability. If that methodology is unreliable, or involves undue delays, the resulting index could hamper rather than help the statutory goal of timely rate increasеs to cover current rail costs. Congress may well have had in mind the difficulties of translating statistical theory into practice when it required the Commission to make only “appropriate” adjustments to its cost index. Thus, while we agree with petitioners that the purpose of section 203 was to allow railroads to keep up with cost increases, we cannot conclude that this purpose mandates adoption of an output index regardless of the accuracy of such an index or the feasibility of designing it so as to allow railroads to obtain rate increases in a timely manner.
B. Application of Section 208
Petitioners argue that even if section 203 does not mandate adoption of an output index, the Commission acted arbitrarily and capriciously by not adjusting the AAR index to reflect productivity growth.
1. Scope of Review
When an agency rule is challenged as arbitrary and capricious, the scope of judicial review is narrow. Courts may not substitute their judgment for that of the agency, see Citizens to Preserve Overton Park v. Volpe,
In this case, the narrowness of our scope of review is reinforced by the narrowness of the Commission’s action. Although the Commission adopted a methodology for indexing rail costs that does not include a specific productivity adjustment, it stated its intention to periodically check the results of its current methodology against other data sources, including its own cost data. See
2. Adequacy of the Commission’s Decision
Despite the narrowness of the issue and the scope of review in this case, we find the Commission’s decision is only minimally adequate. The Commission has not responded to some important comments and has relied, in part, on inappropriate considerations. Nonetheless, it has sketched out a sufficient justification to omit a productivity adjustment from its initial cost indexing methodology.
The crux of the Commission’s rationale is that available productivity measures are sufficiently unreliable, and the consequences of overestimating productivity growth are sufficiently grave, that it is inappropriate to adjust the cost index on the assumption of continued productivity growth. The Commission’s assessment of the unreliability of productivity measures
The difficulties of accurately estimating productivity growth are also reflected in the diverse results of past studies. One study, by Dr. John W. Kendrick, found productivity growth to be as high as 5.2 percent per year. See id. (citing J. W. Kendrick, Post War Productivity Trends in the United States, 1948-1969, 78-79 (1973)), J.A. 512. Another study estimated that average productivity growth was low as 0.8 to 1.8 percent per year. See id. (citing Council on Economic Advisers & National Commission on Productivity, Task Force on Railroad Productivity, Improving Railroad Productivity 78 (1973)), J.A. 512. But even if the Commission could reconcile the expertise in estimating past productivity growth, it is by no means clear that it could develop a satisfactory mechanism for evaluating current productivity trends. This “exercise in applied econometrics” may yield a formula too low in predictive value to be reliable. Furthermore, it may be considerably more difficult to gather the relevant productivity data on a current basis than it is to price items in a market basket. Reliable current estimates, however, are of central importance to section 203’s function of allowing railroads to recover costs promptly. Were the Commission to simply follow the shippers’ suggestions and assume that future productivity trends will match past experience, it could over-deflate the cost index, thereby denying railroads the timely and unencumbered rate increases they deserve.
3. The Commission’s Remaining Justification
More troubling are the Commission’s remaining policy justifications for omitting a productivity adjustment. These policy arguments suggest that the Commission may be taking the position that a productivity adjustment would never be appropriate, or at least would never be appropriate during periods of revenue inadequacy.
a. Penalties for Inefficiency
The Commission’s decision suggests that the effect of a productivity adjustment on railroads with below average productivity performance justifies omitting productivity as a factor in its cost index. The Commission explained that a productivity adjustment would reduce the ability of railroads to recoup their costs even if their below average performance is beyond their control. As a hypothetical example, the Commission posed the case of a productivity breakthrough for bulk commodities. It noted that “such a breakthrough would improve industry average statistics, but would be of little benefit to railroads whose traffic was predominantly nonbulk in nature.”
Petitioners argue that the fallout of any statistical average on individual carriers is
b. Revenue Adequacy
A familiar principle of rate regulation is that regulated rates should approximate rates under competitive conditions. See A. Kahn, 1 The Economics of Regulation 65 (1970). Relying on this principle, shiрpers argued that under competitive conditions, productivity gains would be passed along to consumers. See, e.g., Verified Statement of Leroy E. Peabody, J.A. 820-21. The Commission rejected this justification for a productivity adjustment, reasoning that productivity gains are not passed along to consumers under competitive conditions when a firm’s revenues fail to cover its costs. See
We agree with petitioners that revenue adequacy is not a proper justification for omitting a productivity adjustment. The Staggers Act provides a twofold process for assuring revenue adequacy: an inflationary cost index and a rate flexibility zone for rate increases above costs. Under this two part structure, the purpose of the inflationary cost index is simply to allow railroads to raise their rates to reflect current costs. See pp. 16-20 supra. While the statute does not prohibit adoption of an index that incidentally boosts a railroаd’s net revenues, increasing net revenues is not a proper reason for refusing to make otherwise appropriate adjustments. Nonetheless, as we have observed, the inadequate state of rail revenues does provide the Commission with grounds for caution in the light of the unreliability of productivity measurements. Thus, while we disagree with the Commission that inadequate revenues provide an independent reason for not adjusting the index, We do concede that the Commission properly concluded that an imprecise adjustment would pose greater risks in times of revenue inadequacy.
c. Incentives for Productivity Growth
We also fail to find a reasoned basis for the Commission’s assumption that an average productivity adjustment would undermine incentives for productivity growth. Although the Commission retreated from its original statement that a productivity adjustment would eliminate such incentives, it has continued to assert that a productivity adjustment would have an adverse effect on incentives for productivity growth.
III. CONCLUSION
In affirming the Commission’s order, we share some of the doubts expressed by ICC Chairman Taylor that the modified AAR index may not be precisely the type of index envisioned by the statute. See Ex Parte No. 290 (Sub. No. 2), Railroad Cost Recovery Procedures, Clarification of Decision,
Notes
. The test for market dominance is set forth in section 202 of the Act, 49 U.S.C.A. § 10709(d) (West Supp.1981). See page 918 infra. Pursuant to section 201(a), 49 U.S.C.A. § 10701a(c) (West Supp.1981), the Commission also has jurisdiction to prevent railroads from setting rates below a reasonable minimum.
. After September 30, 1984, market dominance will depend on a “cost recovery percentage.” See 49 U.S.C.A. § 10709(d)(2)(E) (West Supp.1981).
. In contrast, inflationary cost increases authorized under section 206 of the Act, 49 U.S.C.A. § 10712 (West Supp.1981), go into effect automatically unless the railroad applies for an exception.
. Even within the zone of rate flexibility, however, the Commission may investigate a rate increase that results in a revenue-variable cost percentage equal to or in excess of the amounts stated in 49 U.S.C.A. § 10707a(e)(2)(A).
. The total zone of “rate flexibility” for rate increases during the four years following passage of the Act is set at 118 percent of the adjusted base rate. See 49 U.S.C.A. § 10707a(c)(1) (West Supp.1981). For the following four years, the burden of proof lies with the one challenging the rate so long as the rate increase is four percentage points or less of the adjusted base rate. See 49 U.S.C.A. § 10707a(d) (West Supp.1981).
. See 49 U.S.C.A. § 10701a(b)(2)(B) (West Supp.1981). The railroad also bears the burden of proof if its revenue-variable cost percentage equals or exceeds the lesser of the amounts set forth in 49 U.S.C.A. § 10707a(e)(2)(A) (West Supp.1981).
. The Western Coal Traffic League (“WCTL”) estimates that a 2.5 percentage point distortion in the inflation index could lead to “unwarranted rate increases” of $580,000,000 in a single year. See WCTL Brief 3.
. A Laspeyre’s price index weighs price changes according to quantities purchased during the base year. See Ex Parte No. 290 (Sub. No. 2), Railroad Cost Recovery Procedures, Final Rules,
. During this rulemaking proceeding, AAR stated that it was in the process of revising the AAR index. These revisions will delete six of the sixty-five items in the current index, update the weights assigned to the items purchased by railroads and will expand the index’s coverage to include items other than fuel, labor, and materials and supplies. See Verified Statement of Mary Maher, J.A. 441-59. This new “all inclusive” index had not been formulated at the time the ICC decided this case.
.Technically, the term “output index” is not ordinarily associated with an index of cost per unit of output. Instead, the term refers to an index of the prices a firm charges for its output. See United States Department of Labor, BLS Handbook of Methods for Surveys and Studies 123 (1976). Following the usage of the parties, this opinion will use the shorthand formulation “output index” to refer to an index of cost per unit of output.
. The Commission proposed use of the Bureau of Labor Statistics’ Producer Price Index (PPI) to measure those costs not covered in the AAR index, such as depreciation, rents and taxes. See Ex Parte No. 290 (Sub. No. 2), Railroad Cost Recovery Procedures, Notice of Proposed Rulemaking (Nov. 21, 1980), J.A. 591. The Commission’s cost index would be a weighted average of the PPI and the AAR index.
. The Commission proposed to: (1) check for errors in applying the AAR methodology, such as data calculation and transcription mistakes; (2) audit the underlying data provided by railroads; and (3) cross-check the AAR data for internal consistency. J.A. 589.
. WCTL’s brief was also filed on behalf of petitioners in Nos. 81-1480, 81-1523, 81-1547, 81-1590, 81-1639, 81-1642, 81-1659, and 81-1661 and three intervenor-petitioners, Duke Power Company, The National Industrial Traffic League and Virginia Electric Power Company.
. Additional briefs were filed by intervenorpetitioners American Iron and Steel Institute and Central Illinois Light Company and by intervenor Nevada Power Company. An amicus curiae brief urging reversal was filed by the Consumer-Owned Power Coalitiоn.
. Petitioners in Nos. 81-1437, 81-1480, 81-1590 also challenge application of the modified AAR index to rates that contain an element of excess profit. In essence these petitioners would require review of the reasonableness of rates prior to application of the cost adjustment index, even after the 180 day period for challenging rates has expired. The Staggers Act, however, clearly provides that the cost adjustment index may be applied to any market dominant rate that was not challenged within that time period or that withstood such a challenge. See 49 U.S.C.A. § 10707a (West Supp.1981).
In a similar effort to prevent specified rates from rising in accordance with average costs, intervenor Nevada Power Company argues that the Commission should have developed a separate cost index for coal traffic. We fail to see, however, how the statutory mandate to develop an index of rail costs may be read as requiring separate indices for each type of traffic.
. We also question the wisdom of interpreting these words without any reference to the function of the inflationary cost index within the statutory scheme of the Staggers Act. As we discuss, infra, this function is simply to allow railroads to receive timely rate increases to cover inflationary cost increases. The interpretation forwarded by the AAR and the Commission’s attorneys, however, would allow for unreviewable, profit enhancing, rate increases. Moreover, by grounding this interpretation in the language of the statute, these parties would preclude any future attempts by the Commission to correct its index for productivity growth, even if omitting that cost factor causes significant distortions in the index.
. It is noteworthy that no party has directed our attention to an example of an “output” index. Rather than proposing an independent “output” methodology, the shippers seek to have the AAR index adjusted so that it reflects the impact of productivity changes on cost per unit of output.
. We also reject petitioners’ suggestion that the bare language of section 219 precludes use of an input index to determine the permissibility of general rate increases. Section 219 limits antitrust immunity for rate bureaus discussing or voting on railroad rate increases, but provides that these limitations will not apply to “general rate increases to cover inflationary cost increases” until January 1, 1984. See 49 U.S.C.A. § 10706(a)(3)(B) (West Supp.1981). This provision was added in Conference, and is not accompanied by any explanatory legislative history. See H.Rep.No.1430, 96th Cong., 2d Sess. 114 (1980), U.S.Code Cong. & Admin. News 1980, p. 3978. Absent any indication that the term “inflationary cost” was intended to have different meanings in sections 219 and 203, we conclude that it is proper for the Commission to use a valid section 203 index to determine whether general rate increases fall within the immunity provisions of section 219.
. The AAR index is officially entitled an “Index of Railroad Material Prices and Wages,” the same title that S.1946 gave to its inflation index. Thus, it is hardly surprising that some witnesses before the Senate, and the parties in this case, inferred that S.1946 was in effect proposing adoption of the AAR index. See, e.g., 1 Railroad Transportation Policy Act of 1979, Hearings Before the Senate Committee on Commerce, Science, and Transportation on S.1946 428 (1979) (“Senate Hearings ”) (Statement of Ellis Cox); id. at 435 (Statement of Gerald W. Fauth, Jr.). S.1946, however, clearly contemplated the possibility that the Commission would adopt another index since it specified that the index could be “compiled” by the Commission.
. See S.Rep.No.470, 96th Cong., 1st Sess. 52 (1979) (“S.Rep”).
. See, e.g., Senate Hearings 428 (Statement of Ellis Cox); id. at 435 (Statement of Gerald W. Fauth, Jr.); id. at 587 (Statement of L. T. Barringer); id. at 631 (Statement of PPG Industries); id. at 667 (Statement of the National Broiler Council).
. The House bill contained a provision for inflation increases, but did not provide any description of an inflation index. The Conference Committee adopted the Senate’s proposal for computing an adjusted base rate on the basis of a rail cost adjustment factor. See H.Rep.No.1430, 96th Cong., 2d Sess. 93 (1980) (Conference Report).
.Indeed, despite changes in the language of section 203, the Senate Report provided the very same description of the index as Senator Cannon had when he introduced S.1946. Compare S.Rep. at 19-20 with 125 Cong.Rec.S 15315 (daily ed. Oct. 29, 1979).
, See pp. 918-919 supra.
. See, e.g., Senate Hearings 136-37 (Statement of William H. Dempsey) (proposing a “free zone” for rate increases above the bill’s “zone of rail cost inflation”).
. Although the Conference Committee did not explain its reasons for redrafting section 203 to require appropriate adjustments to reflect the “composition of railroad costs, including the quality and mix of material and labor” (emphasis added), this broadening of section 203’s language reinforces the view that the index was intended to allow for all factors bearing on railroad costs.
. CMA also argues that the Commission failed to verify the modified AAR index and failed to provide interested parties with an opportunity to review the data underlying that index. CMA Brief 26-28. Both these contentions misperceive the purpose of the rulemaking in this case. That purpose was to select a general methodology for measuring the impact of inflation on railroad costs, not to actually measure rail cost inflation. The Commission’s “verification” obligation at this initial stage was to assure that the index did not contain unreasonable biases. The Commission fulfilled this obligation by reviewing the AAR index’s methodology and making appropriate adjustments to reflect the composition of railroad costs. See
. Several shipper witnesses argued that even if productivity is hard to measure, the Commission should make some adjustment for productivity growth. This view is well summarized by the Verified Statement of Thomas D. Crowley, submitted by the Western Coal Traffic League:
[W]hile there is no general agreement on precisely what figure represents the long-term change in railroad productivity, it is understood that the proper figure is not zero. Yet, zero is the figure the Commission has in effect adopted. Even an annual change in productivity growth of 1.7 percent, the result reached in one of the studies lauded by the railroads in this proceeding (see Dr. Levine, supra, p. 11), would be better than the figure of zero used by the Commission.
It should be understood that the 1.7 percent figure, while low, would not be insignificant if used as the basis for an adjustment to the AAR Index. This productivity adjustment (1.7 percent) reflects the percentage of overall costs saved by the productivity increases. In other words, if the annual change in the AAR Index equals 6.8 percent, the 1.7 percent increase in productivity would be subtracted from this annual increase resulting in a 25 percent discount in the AAR Index.
Record 135.
This argument, though plausible at first glance, is nonetheless deceptive. Although the comments before the Commission indicated that average long-term productivity growth is greater than zero, there is no support for the conclusion that productivity is bound to grow in any one year. Indeed, the record indicates that as a result of business cycle effects, productivity may temporarily remain at a standstill, or even decline. See Verified Statement of Dr. Paul O. Roberts & Dr. Brian C. Kullman, J.A. 23-25. Thus the record does not support the shippers’ assertion that productivity will always grow at some minimum rate.
. The .Staggers Act required the Commission to publish a rail cost index by the fourth quarter of 1980, and to update the index on at least a quarterly basis. See 49 U.S.C.A. § 10707a(a) (2)(B) (West. Supp.1981). In his concurrence to the Commission’s clarification of its decision in Ex Parte No. 290 (Sub. No. 2 ), Chairman Taylor suggested that this time schedule necessitated adoption of the modified AAR index “for reasons of expediency.”
. As we explained supra, the narrow question before us is whether the Commission adequately justified its decision to omit a productivity adjustment at this time. Having answered this question affirmatively, and recognizing the Commission’s willingness to review the results of its methodology in the future, we give the Commission the benefit of the doubt that it would reevaluate the sweeping implications of its additional policy justifications in the light of its experience.
. Petitioners contend that the Commission abandoned this rationale. See WCTL’s Reply Brief 16. We disagree. In its Notice of Proposed Rulemaking, the Commission stated its view that a prоductivity adjustment would undermine incentives for productivity growth. The statement of reasons accompanying the rule backed off from this view, concluding that “an adjustment based on average productivity gains would not entirely eliminate incentives to railroads with better than average performance.”
. The shippers’ witnesses argued that even railroads with below average performance will have an incentive to improve their own productivity so as to avoid the “penalty” of a rate adjustment below that required to cover costs. See, e.g.. Verified Statement of Carl M. Snavely, Jr., J.A. 709 (“there is as much, if not more, incentive to avoid a penalty than there is to achieve a gain”); Verified Statement of Dr. George H. Borts, J.A. 567 (“It is only on captive traffic that the railroads have a guaranteed market. But even here they would have to raise productivity to remain whole.”); Verified Statement of Jeffrey C. Kline, J.A. 639 (“using regional or national average costs, each carrier would maximize its profits by striving to increase its productivity more than the average level”).
