opinion: Mr. Justice Black
  delivered the opinion of the Court.
  The question presented by this case is whether the FTC was warranted in finding that it was an unfair method of competition in violation of § 5 of the Federal Trade Commission Act, 38 Stat. 719, as amended, 15 U. S. C. § 45, for respondent Texaco to undertake to induce its service station dealers to purchase Goodrich tires, batteries, and accessories (hereafter referred to as TBA) in return for a commission paid by Goodrich to Texaco. In three related proceedings instituted in 1961, the Commission challenged the sales-commission method of distributing TBA and in each case named as a respondent a major oil company and a major tire manufacturer. After extensive hearings, the Commission concluded that each of the arrangements constituted an unfair method of competition and ordered each tire company and each oil company to refrain from entering into any such commission arrangements. In one of these cases, Atlantic Refining Co. v. FTC, 381 U. S. 357 (1965), this Court affirmed the decision of the Court of Appeals for the Seventh Circuit sustaining the Commission's order against Atlantic Refining Company and the Goodyear Tire & Rubber Company. In a second case, Shell Oil Co. v. FTC, 360 F. 2d 470, cert. denied, 385 U. S. 1002, the Court of Appeals for the Fifth Circuit, following this Court’s decision in Atlantic, sustained the Commission’s order against the Shell Oil Company and the Firestone Tire & Rubber Company. In contrast to the decisions of these two Courts of Appeals, the Court of Appeals for the District of Columbia Circuit set aside the Commission’s order in this, the third of the three cases, involving respondents Goodrich and Texaco. 118 U. S. App. D. C. 366, 336 F. 2d 754 (1964). The Commission petitioned this Court for review and, one week following our Atlantic decision, we granted certiorari and remanded for further consideration in light of that opinion. 381 U. S. 739 (1965). The Commission, on remand, reaffirmed its conclusion that the Texaco-Goodrich arrangement, like that involved in the other two cases, violated § 5 of the Federal Trade Commission Act. The Court of Appeals for the District of Columbia Circuit again reversed, this time holding that the Commission had failed to establish that Texaco had exercised its dominant economic power over its dealers or that the Texaco-Goodrich arrangement had an adverse effect on competition. 127 ü. S. App. D. C. 349, 383 F. 2d 942. We granted certiorari to determine whether the court below had correctly applied the principles of our Atlantic decision. 390 U. S. 979.
  Congress enacted § 5 of the Federal Trade Commission Act to combat in their incipiency trade practices that exhibit a strong potential for stifling competition. In large measure the task of defining “unfair methods of competition” was left to the Commission. The legislative history shows that Congress concluded that the best check on unfair competition would be “an administrative body of practical men . . . who will be able to apply the rule enacted by Congress to particular business situations, so as to eradicate evils with the least risk of interfering with legitimate business operations.” H. R. Conf. Rep. No. 1142, 63d Cong., 2d Sess., 19. Atlantic Refining Co. v. FTC, 381 U. S. 357, 367. While the ultimate responsibility for the construction of this statute rests with the courts, we have held on many occasions that the determinations of the Commission, an expert body charged with the practical application of the statute, are entitled to great weight. FTC v. Motion Picture Advertising Serv. Co., 344 U. S. 392, 396 (1953); FTC v. Cement Institute, 333 U. S. 683, 720 (1948). This is especially true here, where the Commission has had occasion in three related proceedings to study and assess the effects on competition of the sales-commission arrangement for marketing TBA. With this in mind, we turn to the facts of this case.
  The Commission and the respondents agree that the Texaco-Goodrich arrangement for marketing TBA will fall under the rationale of our Atlantic decision if the Commission was correct in its three ultimate conclusions (1) that Texaco has dominant economic power over its dealers; (2) that Texaco exercises that power over its dealers in fulfilling its agreement to promote and sponsor Goodrich products; and (3) that anticompetitive effects result from the exercise of that power.
  That Texaco holds dominant economic power over its dealers is clearly shown by the record in this case. In fact, respondents do not contest the conclusion of the Court of Appeals below and the Court of Appeals for the Fifth Circuit in Shell that such power is “inherent in the structure and economics of the petroleum distribution system.” 127 U. S. App. D. C. 349, 353, 383 F. 2d 942, 946; 360 F. 2d 470, 481 (C. A. 5th Cir.). Nearly 40% of the Texaco dealers lease their stations from Texaco. These dealers typically hold a one-year lease on their stations, and these leases are subject to termination at the end of any year on 10 days’ notice. At any time during the year a man’s lease on his service station may be immediately terminated by Texaco without advance notice if in Texaco’s judgment any of the “housekeeping” provisions of the lease, relating to the use and appearance of the station, are not fulfilled. The contract under which Texaco dealers receive their vital supply of gasoline and other petroleum products also runs from year to year and is terminable on 30 days’ notice under Texaco’s standard form contract. The average dealer is a man of limited means who has what is for him a sizable investment in his station. He stands to lose much if he incurs the ill will of Texaco. As Judge Wisdom wrote in Shell, “A man operating a gas station is bound to be overawed by the great corporation that is his supplier, his banker, and his landlord.” 360 F. 2d 470, 487.
  It is against the background of this dominant economic power over the dealers that the sales-commission arrangement must be viewed. The Texaco-Goodrich agreement provides that Goodrich will pay Texaco a commission of 10% on all purchases by Texaco retail service station dealers of Goodrich TBA. In return, Texaco agrees to “promote the sale of Goodrich products” to Texaco dealers. During the five-year period studied by the Commission (1952-1956) $245,000,000 of the Goodrich and Firestone TBA sponsored by Texaco was purchased by Texaco dealers, for which Texaco received almost $22,000,000 in retail and wholesale commissions. Evidence before the Commission showed that Texaco carried out its agreement to promote Goodrich products through constantly reminding its dealers of Texaco’s desire that they stock and sell the sponsored Goodrich TBA. Texaco emphasizes the importance of TBA and the recommended brands as early as its initial interview with a prospective dealer and repeats its recommendation through a steady flow of campaign materials utilizing Goodrich products. Texaco salesmen, the primary link between Texaco and the dealers, promote Goodrich products in their day-to-day contact with the Texaco dealers. The evaluation of a dealer’s station by the Texaco salesman is often an important factor in determining whether a dealer’s contract or lease with Texaco will be renewed. Thus the Texaco salesmen, whose favorable opinion is so important to every dealer, are the key men in the promotion of Goodrich products, and on occasion accompany the Goodrich salesmen in their calls on the dealers. Finally, Texaco receives regular reports on the amount of sponsored TBA purchased by each dealer. Respondents contend, however, that these reports are used only for maintaining Texaco’s accounts with Goodrich and not for policing dealer purchases.
  Respondents urge that the facts of this case are fundamentally different from those involved in Atlantic because of the presence there, and the absence here, of “overt coercive practices” designed to force the dealers to purchase the sponsored brand of TBA. We agree, as the Government concedes, that the evidence in this case regarding coercive practices is considerably less substantial than the evidence presented in Atlantic. The Atlantic record contained direct evidence of dealers threatened with cancellation of their leases, the setting of dealer quotas for purchase of certain amounts of sponsored TBA, the requirement that dealers purchase TBA from single assigned supply points, refusals by Atlantic to honor credit card charges for nonsponsored TBA, and policing of Atlantic dealers by “phantom inspectors.” While the evidence in the present case fails to establish the kind of overt coercive acts shown in Atlantic, we think it clear nonetheless that Texaco’s dominant economic power was used in a manner which tended to foreclose competition in the marketing of TBA. The sales-commission system for marketing TBA is inherently coercive. A service station dealer whose very livelihood depends upon the continuing good favor of a major oil company is constantly aware of the oil company’s desire that he stock and sell the recommended brand of TBA. Through the constant reminder of the Texaco salesman, through demonstration projects and promotional materials, through all of the dealer’s contacts with Texaco, he learns the lesson that Texaco wants him to purchase for his station the brand of TBA which pays Texaco 10% on every retail item the dealer buys. With the dealer’s supply of gasoline, his lease on his station, and his Texaco identification subject to continuing review, we think it flies in the face of common sense to say, as Texaco asserts, that the dealer is “perfectly free” to reject Texaco’s chosen brand of TBA. Equally applicable here is this Court’s judgment in Atlantic that “[i]t is difficult to escape the conclusion that there would have been little point in paying substantial commissions to oil companies were it not for their ability to exert power over their wholesalers and dealers.” 381 U. S., at 376.
  We are similarly convinced that the Commission was correct in determining that this arrangement has an adverse effect on competition in the marketing of TBA. Service stations play an increasingly important role in the marketing of tires, batteries, and other automotive accessories. With five major companies supplying virtually all of the tires that come with new cars, only in the replacement market can the smaller companies hope to compete. Ideally, each service station dealer would stock the brands of TBA that in his judgment were most favored by customers for price and quality. To the extent that dealers are induced to select the sponsored brand in order to maintain the good favor of the oil company upon which they are dependent, the operation of the competitive market is adversely affected. As we noted in Atlantic, the essential anticompetitive vice of such an arrangement is “the utilization of economic power in one market to curtail competition in another.” 381 U. S. 357, 369. Here the TBA manufacturer has purchased the oil company’s economic power and used it as a partial substitute for competitive merit in gaining a major share of the TBA market. The nonsponsored brands do not compete on the even terms of price and quality competition; they must overcome, in addition, the influence of the dominant oil company that has been paid to induce its dealers to buy the recommended brand. While the success of this arrangement in foreclosing competitors from the TBA market has not matched that of the direct coercion employed by Atlantic, we feel that the anticompetitive tendencies of such a system are clear, and that the Commission was properly fulfilling the task that Congress assigned it in halting this practice in its incipiency. The Commission is not required to show that a practice it condemns has totally eliminated competition in the relevant market. It is enough that the Commission found that the practice in question unfairly burdened competition for a not insignificant volume of commerce. International Salt Co. v. United States, 332 U. S. 392 (1947); United States v. Loew’s, Inc., 371 U. S. 38, 45, n. 4 (1962); Atlantic Refining Co. v. FTC, 381 U. S. 357, 371 (1965).
  The Commission was justified in concluding that more than an insubstantial amount of commerce was involved. Texaco is one of the Nation’s largest petroleum companies. It sells its products to approximately 30,000 service stations, or about 16.5% of all service stations in the United States. The volume of sponsored TBA purchased by Texaco dealers in the five-year period 1952-1956 was $245,000,000, almost five times the amount involved in the Atlantic case.
  For the reasons stated above, we reverse the judgment below and remand to the Court of Appeals for enforcement of the Commission’s order with the exception of paragraphs five and six of the order against Texaco, the setting aside of which by the Court of Appeals the Government does not contest.
  Reversed and remanded.
  The sales-commission arrangement between Texaco and the Firestone Tire & Rubber Company was also the subject of Commission action. Firestone is not a respondent in this action, however, since it is already subject to a final order of the Commission prohibiting its use of a sales-commission plan with any oil company. See Shell Oil Co. v. FTC, 360 F. 2d 470, 474 (C. A. 5th Cir.), cert. denied, 385 U. S. 1002.
  The Commission’s conclusion that under a sales-commission plan, a dealer would not make his choice solely on the basis of competitive merit was bolstered by the testimony of 31 sellers of competing, nonsponsored TBA that they were unable to sell to particular Texaco stations because of the dealers’ concern that Texaco would disapprove of their purchase of nonsponsored products.
choices: attorney general of the United States, or his office specified state board or department of education city, town, township, village, or borough government or governmental unit state commission, board, committee, or authority county government or county governmental unit, except school district court or judicial district state department or agency governmental employee or job applicant female governmental employee or job applicant minority governmental employee or job applicant minority female governmental employee or job applicant not listed among agencies in the first Administrative Action variable retired or former governmental employee U.S. House of Representatives interstate compact judge state legislature, house, or committee local governmental unit other than a county, city, town, township, village, or borough governmental official, or an official of an agency established under an interstate compact state or U.S. supreme court local school district or board of education U.S. Senate U.S. senator foreign nation or instrumentality state or local governmental taxpayer, or executor of the estate of state college or university United States State person accused, indicted, or suspected of crime advertising business or agency agent, fiduciary, trustee, or executor airplane manufacturer, or manufacturer of parts of airplanes airline distributor, importer, or exporter of alcoholic beverages alien, person subject to a denaturalization proceeding, or one whose citizenship is revoked American Medical Association National Railroad Passenger Corp. amusement establishment, or recreational facility arrested person, or pretrial detainee attorney, or person acting as such;includes bar applicant or law student, or law firm or bar association author, copyright holder bank, savings and loan, credit union, investment company bankrupt person or business, or business in reorganization establishment serving liquor by the glass, or package liquor store water transportation, stevedore bookstore, newsstand, printer, bindery, purveyor or distributor of books or magazines brewery, distillery broker, stock exchange, investment or securities firm construction industry bus or motorized passenger transportation vehicle business, corporation buyer, purchaser cable TV car dealer person convicted of crime tangible property, other than real estate, including contraband chemical company child, children, including adopted or illegitimate religious organization, institution, or person private club or facility coal company or coal mine operator computer business or manufacturer, hardware or software consumer, consumer organization creditor, including institution appearing as such; e.g., a finance company person allegedly criminally insane or mentally incompetent to stand trial defendant debtor real estate developer disabled person or disability benefit claimant distributor person subject to selective service, including conscientious objector drug manufacturer druggist, pharmacist, pharmacy employee, or job applicant, including beneficiaries of employer-employee trust agreement, employee health and welfare fund, or multi-employer pension plan electric equipment manufacturer electric or hydroelectric power utility, power cooperative, or gas and electric company eleemosynary institution or person environmental organization employer. If employer's relations with employees are governed by the nature of the employer's business (e.g., railroad, boat), rather than labor law generally, the more specific designation is used in place of Employer. farmer, farm worker, or farm organization father female employee or job applicant female movie, play, pictorial representation, theatrical production, actor, or exhibitor or distributor of fisherman or fishing company food, meat packing, or processing company, stockyard foreign (non-American) nongovernmental entity franchiser franchisee lesbian, gay, bisexual, transexual person or organization person who guarantees another's obligations handicapped individual, or organization of devoted to health organization or person, nursing home, medical clinic or laboratory, chiropractor heir, or beneficiary, or person so claiming to be hospital, medical center husband, or ex-husband involuntarily committed mental patient Indian, including Indian tribe or nation insurance company, or surety inventor, patent assigner, trademark owner or holder investor injured person or legal entity, nonphysically and non-employment related juvenile government contractor holder of a license or permit, or applicant therefor magazine male medical or Medicaid claimant medical supply or manufacturing co. racial or ethnic minority employee or job applicant minority female employee or job applicant manufacturer management, executive officer, or director, of business entity military personnel, or dependent of, including reservist mining company or miner, excluding coal, oil, or pipeline company mother auto manufacturer newspaper, newsletter, journal of opinion, news service radio and television network, except cable tv nonprofit organization or business nonresident nuclear power plant or facility owner, landlord, or claimant to ownership, fee interest, or possession of land as well as chattels shareholders to whom a tender offer is made tender offer oil company, or natural gas producer elderly person, or organization dedicated to the elderly out of state noncriminal defendant political action committee parent or parents parking lot or service patient of a health professional telephone, telecommunications, or telegraph company physician, MD or DO, dentist, or medical society public interest organization physically injured person, including wrongful death, who is not an employee pipe line company package, luggage, container political candidate, activist, committee, party, party member, organization, or elected official indigent, needy, welfare recipient indigent defendant private person prisoner, inmate of penal institution professional organization, business, or person probationer, or parolee protester, demonstrator, picketer or pamphleteer (non-employment related), or non-indigent loiterer public utility publisher, publishing company radio station racial or ethnic minority person or organization protesting racial or ethnic segregation or discrimination racial or ethnic minority student or applicant for admission to an educational institution realtor journalist, columnist, member of the news media resident restaurant, food vendor retarded person, or mental incompetent retired or former employee railroad private school, college, or university seller or vendor shipper, including importer and exporter shopping center, mall spouse, or former spouse stockholder, shareholder, or bondholder retail business or outlet student, or applicant for admission to an educational institution taxpayer or executor of taxpayer's estate, federal only tenant or lessee theater, studio forest products, lumber, or logging company person traveling or wishing to travel abroad, or overseas travel agent trucking company, or motor carrier television station union member unemployed person or unemployment compensation applicant or claimant union, labor organization, or official of veteran voter, prospective voter, elector, or a nonelective official seeking reapportionment or redistricting of legislative districts (POL) wholesale trade wife, or ex-wife witness, or person under subpoena network slave slave-owner bank of the united states timber company u.s. job applicants or employees Army and Air Force Exchange Service Atomic Energy Commission Secretary or administrative unit or personnel of the U.S. Air Force Department or Secretary of Agriculture Alien Property Custodian Secretary or administrative unit or personnel of the U.S. Army Board of Immigration Appeals Bureau of Indian Affairs Bonneville Power Administration Benefits Review Board Civil Aeronautics Board Bureau of the Census Central Intelligence Agency Commodity Futures Trading Commission Department or Secretary of Commerce Comptroller of Currency Consumer Product Safety Commission Civil Rights Commission Civil Service Commission, U.S. Customs Service or Commissioner of Customs Defense Base Closure and REalignment Commission Drug Enforcement Agency Department or Secretary of Defense (and Department or Secretary of War) Department or Secretary of Energy Department or Secretary of the Interior Department of Justice or Attorney General Department or Secretary of State Department or Secretary of Transportation Department or Secretary of Education U.S. Employees' Compensation Commission, or Commissioner Equal Employment Opportunity Commission Environmental Protection Agency or Administrator Federal Aviation Agency or Administration Federal Bureau of Investigation or Director Federal Bureau of Prisons Farm Credit Administration Federal Communications Commission (including a predecessor, Federal Radio Commission) Federal Credit Union Administration Food and Drug Administration Federal Deposit Insurance Corporation Federal Energy Administration Federal Election Commission Federal Energy Regulatory Commission Federal Housing Administration Federal Home Loan Bank Board Federal Labor Relations Authority Federal Maritime Board Federal Maritime Commission Farmers Home Administration Federal Parole Board Federal Power Commission Federal Railroad Administration Federal Reserve Board of Governors Federal Reserve System Federal Savings and Loan Insurance Corporation Federal Trade Commission Federal Works Administration, or Administrator General Accounting Office Comptroller General General Services Administration Department or Secretary of Health, Education and Welfare Department or Secretary of Health and Human Services Department or Secretary of Housing and Urban Development Interstate Commerce Commission Indian Claims Commission Immigration and Naturalization Service, or Director of, or District Director of, or Immigration and Naturalization Enforcement Internal Revenue Service, Collector, Commissioner, or District Director of Information Security Oversight Office Department or Secretary of Labor Loyalty Review Board Legal Services Corporation Merit Systems Protection Board Multistate Tax Commission National Aeronautics and Space Administration Secretary or administrative unit of the U.S. Navy National Credit Union Administration National Endowment for the Arts National Enforcement Commission National Highway Traffic Safety Administration National Labor Relations Board, or regional office or officer National Mediation Board National Railroad Adjustment Board Nuclear Regulatory Commission National Security Agency Office of Economic Opportunity Office of Management and Budget Office of Price Administration, or Price Administrator Office of Personnel Management Occupational Safety and Health Administration Occupational Safety and Health Review Commission Office of Workers' Compensation Programs Patent Office, or Commissioner of, or Board of Appeals of Pay Board (established under the Economic Stabilization Act of 1970) Pension Benefit Guaranty Corporation U.S. Public Health Service Postal Rate Commission Provider Reimbursement Review Board Renegotiation Board Railroad Adjustment Board Railroad Retirement Board Subversive Activities Control Board Small Business Administration Securities and Exchange Commission Social Security Administration or Commissioner Selective Service System Department or Secretary of the Treasury Tennessee Valley Authority United States Forest Service United States Parole Commission Postal Service and Post Office, or Postmaster General, or Postmaster United States Sentencing Commission Veterans' Administration War Production Board Wage Stabilization Board General Land Office of Commissioners Transportation Security Administration Surface Transportation Board U.S. Shipping Board Emergency Fleet Corp. Reconstruction Finance Corp. Department or Secretary of Homeland Security Unidentifiable International Entity