NELSON, J., delivered the opinion of the court, in which HOOD, D.J., joined. GUY, J. (pp. 830-37), delivered a separate dissenting opinion.
DAVID A. NELSON, Circuit Judge.
The question presented here is whether the United States Internal Revenue Code imposes a tax on investment income realized by the Michigan Education Trust. The trust is a state agency established to receive advance payménts of college tuition, invest the money, and ultimately make disbursements under a program that lets its beneficiaries attend any of the state’s public colleges or universities without further tuition cost.
The district court held the education trust liable for federal income taxes. 802 F.Supp. 120. We conclude that while Congress could, if it wished, tax the investment income of state agencies such as the education trust, it has not chosen to do so. Accordingly, we shall reverse the judgment of the district court.
I
The Michigan Education Trust, created by an act of the Michigan legislature signed into law by the governor on December 23, 1986,1 is “a public body corporate and politic.” M.C.L.A. 390.1425, § 5(1) of the act. As such, the education trust is a public instrumentality of the state. The grant of corporate powers to such an agency makes it “a quasi corporation” under Michigan law, see Advisory Opinion re Constitutionality of PA 1966, No. 346, 380 Mich. 554, 575, 158 N.W.2d 416, 425 (1968), but the agency “remains an instrumentality of the State.” Id.
The Michigan Constitution provides, subject to exceptions not relevant here, that each of the “agencies and instrumentalities of the executive branch of state government” must “be allocated by law” to one of the principal departments of the executive branch. Mich. Const., Art. V, § 2. Pursuant to this constitutional requirement, § 5(1) of the Education Trust Act, M.C.L.A. § 390.1425, provides that the education trust “shall be within the department of treasury. ...”
Like many government agencies vested with corporate powers, the education trust has a board of directors by which such powers are exercised. Id. (Among the powers of this particular board is an express statuto[819]*819ry power to “[ejnter into contracts on behalf of the state.” M.C.L.A. § 390.1431, § ll(k) of the act.) The state treasurer is a member of the education trust’s board ex officio, and the other board members (eight in number) are appointed by the governor with the advice and consent of the senate. M.C.L.A. § 390.1430, § 10(1) of the act.
Although the education trust is “within” the treasury department, and although the state treasurer (who is the head of that department) serves as a member of the board, the board acts “independently” of the treasury department. M.C.L.A. § 390.1425, § 5(1) of the act. For certain state constitutional purposes, and for purposes of the law governing payment of full-faith-and-eredit obligations of the state, M.C.L.A. § 12.61 et seq., assets of the education trust are not considered state money, common cash, or revenue of the state. M.C.L.A. § 390.1429, § 9(2) of the act. (This technical provision means, among other things, that the education trust has broader investment powers than would otherwise be available to it.)
Trust assets may be invested in any manner the trust deems appropriate, and may be pooled for investment purposes with state pension funds and other investments of the state. M.C.L.A. § 390.1429, § 9(4) of the act. It is state employees who invest education trust assets, and trust funds are paid out only through State of Michigan checks or warrants. All income of the education trust is exempt from state income taxes. M.C.L.A. § 390.1435, § 15 of the act. Michigan’s auditor general is responsible for auditing the books of the education trust, and the board must submit an annual accounting to the governor and leaders of the Michigan legislature. M.C.L.A. § 390.1432, § 12 of the' act. Legal representation is provided to the education trust by the Attorney General of the State of Michigan.
The business of the education trust’s board must be conducted in compliance with Michigan’s Open Meetings Act, and the education trust is likewise subject to the state’s Freedom of Information Act. M.C.L.A. § 390.1430, §§ 10(5) and 10(6) of the act. All education trust employees are members of the classified civil service of the state; as civil servants, they are subject to state civil service commission rules and regulations. Advance tuition payments collected by the education trust are deposited in a bank trust account under the name of the State Treasurer, State of Michigan, Agent for the Michigan Education Trust. Assets of the trust are earmarked for uses set forth in the statute, including the making of payments to state institutions of higher education on behalf of qualified beneficiaries. M.C.L.A. § 390.1429, § 9(3) of the act.
The Michigan attorney general’s department has advised the board of the education trust that the trust is an “agency” of the State of Michigan. The attorney general’s department has further advised that the members of the board are “public officers” for purposes of the Michigan Governmental Liability for Negligence Act.
Before we turn to the purposes for which the education trust was created, it will be useful to refer to a bit of early history. On July 13, 1787 — two years before the Constitution of the United States was adopted and 50 years before the State of Michigan was admitted to the Union — Congress enacted the Northwest Ordinance. Captioned “An Ordinance for the Government of the Territory of the United States Northwest of the River Ohio,” this landmark legislation— which was to have a profoundly important effect on the subsequent development of both state and national law — was the fundamental instrument of government for an area covering more than a quarter of a million square miles. The territory to which the ordinance applied included all of present-day Michigan, plus Indiana, Illinois, Wisconsin, Ohio, and part of Minnesota.
Article III of the Northwest Ordinance began with this famous sentence: “Religion, morality, and knowledge being necessary to good government and the happiness of mankind, schools and the means of education shall forever be encouraged.” The framers of both of Michigan’s 20th Century constitutions — the first adopted in 1908 and the second in 1963 — included articles on education in which the opening language mirrored the language of the first sentence of Article III of the Northwest Ordinance. Thus Article [820]*820VIII, § 1 of Michigan’s present constitution, adopted without change from Article IX, § 1 of the constitution of 1908, perpetuates, as part of the state’s basic law, the principle that “schools and the means of education shall forever be encouraged.”
As part of Michigan’s efforts to make “the means of education” available to its citizens, the state maintains an extensive system of public colleges and universities. (The University of Michigan and Michigan State University are but two of a rather long list of such , institutions.) Financial support for these public colleges and universities comes from a variety of sources, including both appropriations from the legislature and tuition payments.
During the first half of the decade of the 1980s, tuition costs at Michigan’s public institutions of higher education, like tuition costs at public and private colleges throughout the nation, increased at rates that many found alarming. (Over the decade as a whole, the average tuition at Michigan’s four-year colleges and universities more than doubled.) In January of 1986, responding to concern about soaring tuition costs, Michigan’s governor proposed in his State of the State Address that Michigan adopt a state-run prepaid tuition program “designed to help parents guarantee to their children the opportunity of a Michigan college education.” 1986 Mich. Journal of the House 152. The Michigan Education Trust Act was the embodiment of that proposal.
The act contained an extensive set of legislative findings, beginning with one that the attentive reader will find familiar: “It is an essential function of state government to forever encourage schools and the means of education, as provided in section 1 of article VIII of the state constitution of 1963.” M.C.L.A. § 390.1422, § 2(a) of the act. The legislature further found it to be “an essential function of state government to encourage attendance at state institutions of higher education,” § 2(c); noted that “[s]tudents in elementary and secondary schools tend to achieve to a higher standard of performance when the payment of tuition for their higher education is secured,” § 2(h); and declared that “[providing assistance to assure the higher education of the citizens of this state is necessary and desirable for the public health, safety, and welfare,” § 2(i).
In light of these and other findings, the legislature declared the purposes of the act (and of the education trust) to be as follows:
“(a) To encourage education and the means of education.
(b) To maintain state institutions of higher education by helping to provide a stable financial base to these institutions.
(c) To provide wide and affordable access to state institutions of higher education for the residents of this state.
(d) To encourage attendance at state institutions of higher education.
(e) To provide students and their parents economic protection against rising tuition costs.
(f) To provide students and their parents financing assistance for postsecondary education at a Michigan institution of higher education of their choice.
(g) To help provide the benefits of higher education to the people of this state.
(h) To encourage elementary and secondary students in this state to achieve high standards of performance.” M.C.L.A. § 390.1423, § 3 of the act.
The manner in which the education trust operates is relatively simple in concept. Acting on behalf of the state and itself (see M.C.L.A. § 390.1426, § 6(1) of the act), the trust enters into advance tuition payment' contracts with parents, grandparents, or anyone else who wants assurance that tuition costs for a particular beneficiary will be covered when the time comes for the beneficiary to enter college. The purchaser pays the trust a stipulated sum — determined on the basis of various actuarial assumptions and forecasts — that reflects the number of years for which tuition is to be prepaid and the number of years remaining before the beneficiary (who must be a Michigan resident at the time of the contract) is expected to enter college.
The trust invests all of the funds so collected. If the beneficiary ultimately enrolls as a Michigan resident in a Michigan public col[821]*821lege or university — and the contract does not guarantee that the beneficiary will be admitted, of course, although we are told that by January of 1993 more than 85 percent of the education trust beneficiaries who had graduated from high school had been admitted to a state college or university — the trust is obligated to use the funds it controls to pay the beneficiary’s full tuition cost, whatever that cost turns out to be. If the beneficiary is no longer a Michigan resident, he is responsible for the difference between the in-state rate and the out-of-state rate.
If the beneficiary reaches the age of 18 and certifies that he will attend a private college within the state, or will attend a college outside the state, or has decided not to attend college at all, the trust is obligated to pay a refund (which, at the beneficiary’s option, may go directly to a designated college or university) in an amount determined under a contractual formula covering that particular contingency. The refund formulas are designed to encourage attendance at some college, as opposed to not enrolling anywhere, but the trust does not promise to cover full tuition costs at any institution other than a public college or university in Michigan.
II
In 1988, before any advance tuition payment contracts had been entered into, the Treasurer of the State of Michigan requested a “no action” letter from the Securities and Exchange Commission.2 The state treasurer’s letter to the SEC submitted that the education trust was a “public instrumentality” the contracts of which, if deemed to be securities, would be exempt from registration under the Securities Act of 1933 pursuant to § 3(a)(2) of that act, 15 U.S.C. § 77c(a)(2). The SEC responded favorably, the agency’s corporate finance division stating that it would not recommend any enforcement action.
The state was also required to request a ruling from the Internal Revenue Service, pursuant to the following provision in the Education Trust Act: “An advance tuition payment contract shall not be entered into by the trust until the internal revenue service has issued a favorable ruling or opinion that the purchaser of the advance payment contract will not be considered actually or constructively to be in receipt of income.” M.C.L.A. § 390.1433, § 13(3) of the act. Joined by a prospective participant in the advance tuition payment program, the Treasurer of the State of Michigan requested such a ruling by letter dated February 19, 1987. The letter also asked for a ruling that “[t]he accrued investment income of the Trust is exempt from federal income taxation pursuant to either the Doctrine of Intergovernmental Tax Immunity or the provisions of Section 115(1) of the Code [26 U.S.C. § 115(1)].”3
In Private Letter Ruling 88-25-027, dated March 29, 1988, the IRS responded with good news and bad news. The good news was that no income would be realized by the purchaser or the beneficiary when an advance tuition payment contract was executed — although income would be realized later on if the value of any subsequently-received educational services or refund exceeded the amount initially paid. The bad news, from the state’s standpoint, was that the trust’s investment income would be subject to federal income tax.
Following receipt of this ruling, the education trust applied to the IRS for recognition of exemption from taxation under § 501(e)(3) of the Internal Revenue Code, 26 U.S.C. § 501(c)(3). (That section exempts corporations and foundations organized and operated exclusively for charitable, educational, or other designated purposes, pro[822]*822vided that no part of the organization’s net earnings inures to the benefit of any private shareholder or individual.) By letter dated April 26, 1989, the IRS replied that it had concluded that the education trust did not qualify for exemption under § 501(c)(3). A final adverse ruling on the education trust’s application for tax exempt status under this section was issued on August 8, 1989.
The education trust paid a federal income tax of $4,495 on investment income realized in the fiscal year ending September 30,1988. A claim for refund followed. More than six months elapsed without a response (see 26 U.S.C. § 6532(a)(1), which gives the IRS up to six months to render a decision on such a claim), and in May of 1990 the education trust, joined by the State of Michigan, commenced the present refund action in the United States District Court for the Western District of Michigan. The parties subsequently stipulated that the trust reported a tax of $7,057,565 on income for the fiscal year ending September 30, 1989, and a tax of $8,768,644 on income for the fiscal year ending September 30, 1990.
Ruling on cross-motions for summary judgment, the district court held the education trust liable for the taxes. The plaintiffs had argued that the Internal Revenue Code was not intended to apply to states or their instrumentalities, but the district court rejected this argument on the theory that the education trust is not an integral part of the State of Michigan. Section 115 was held inapplicable on either or both of two theories: the education trust is not a state or a political subdivision thereof, and the income of the trust does not “accrue” to the state in a bookkeeping sense. With regard to § 501(c)(3) and § 501(c)(4),4 the court held that “because the Trust’s sole direct benefit inures only to individuals who purchase contracts,” the service provided by the education trust “constitutes a substantial private purpose that destroys the Trust’s exemption.” The court also rejected contentions that the education trust was exempt from taxation under the intergovernmental tax immunity doctrine, the Tenth Amendment to the Constitution, and the provision in Article IV, § 4 of the Constitution requiring the United States to guarantee every state “a Republican Form of Government....” An order granting summary judgment in favor of the United States was entered on August 3,1992, and the plaintiffs subsequently filed a timely notice of appeal.
Ill
The state and the education trust have now abandoned the argument that the federal government lacks constitutional authority to impose a tax on investment income produced in the operation of state programs such as that conducted by the education trust. This was an appropriate move, we believe. The broad constitutional immunity from federal taxation once thought to be enjoyed by states and their instrumentalities has been severely eroded with the passage of time, and several years ago the Supreme Court suggested that it is now an open question whether there is “any” extent “to which States are currently immune from direct non-discriminatory federal taxation.” South Carolina v. Baker, 485 U.S. 505, 518 n. 11, 108 S.Ct. 1355, 1364, 99 L.Ed.2d 592 (1988).
It used to be thought that public instrumentalities of a state were constitutionally immune from taxation insofar as they performed a “governmental function,” as opposed to performing a proprietary or “business” function. See, e.g., Allen v. Regents of the University System of Georgia, 304 U.S. 439, 58 S.Ct. 980, 82 L.Ed. 1448 (1938) (federal excise tax could be imposed on sales of tickets to University of Georgia football games, the state having embarked on a business that would normally be taxable); South Carolina v. United States, 199 U.S. 437, 26 S.Ct. 110, 50 L.Ed. 261 (1905) (United States could impose license taxes on state-run liquor business). But the constitutionally-based governmental function/proprietary function test produced “uncertainty and instability” that finally led the Supreme Court to abandon it in State of New York v. United States, [823]*823326 U.S. 572, 66 S.Ct. 310, 90 L.Ed. 326 (1946). Although there was no majority opinion in State of New York, the Court was unanimous in concluding that the test must be abandoned. See Garcia v. San Antonio Metropolitan Transit Authority, 469 U.S. 528, 542, 105 S.Ct. 1005, 1013, 83 L.Ed.2d 1016 (1985), which so states. Accordingly, we are confident that today’s Supreme Court would say that Congress is free to impose a non-discriminatory tax on the investment income at issue here if it wants to. The question we must decide is whether Congress has done so.
Section 11(a) of the Internal Revenue Code, 26 U.S.C. § 11(a), provides that “[a] tax is hereby imposed for each taxable year on the taxable income of every corporation.” The education trust is only a “quasi corporation” under Michigan law, but the reference in § 11(a) to “every corporation” appears, on its face, to be very broad indeed. If one were to read § 11(a) in a vacuum, one might well conclude that the tax imposed by this section extends to the income of all government corporations, “quasi ” or otherwise, including the income of all cities and towns organized as bodies corporate; the income of all public universities such as the University of Michigan and Michigan State University (bodies corporate under Article 8, § 5 of the Michigan constitution); and the income of such federal instrumentalities as the Commodity Credit Corporation, the Export-Import Bank of the United States, the Pension Benefit Guaranty Corporation, the St. Lawrence Seaway Development Corporation, and the Tennessee Valley Authority. (As to the latter group, see 31 U.S.C. § 9101(3), which lists these and various other federal agencies as “wholly owned Government eorporation[s].”)
The United States does not contend, of course, that § 11(a) should be read in a vacuum. As a matter of history, the appel-lee’s brief acknowledges, this section has never been interpreted as imposing a tax on income earned directly by a state, a political subdivision of a state, or “an integral part of a State.” See, in this connection, Internal Revenue Bureau General Counsel Memorandum 14,407, XIV-1 Cum.Bull. 103 (1935), where the Internal Revenue Bureau concluded almost 60 years ago that a state or political subdivision is not a “corporation” for purposes of the Internal Revenue Code.5 See also Rev.Rul. 71-131, 1971-1 Cum.Bull. 28 (superseding GCM 14,407, and reaffirming that income derived from the operation of liquor stores by the State of Montana is not subject to federal income tax); Rev.Rul. 71-132, 1971-1 Cum.Bull. 29 (holding that income derived from the operation of liquor stores by the Oregon Liquor Control Commission is not subject to federal income tax); and Rev.Rul. 87-2, 1987-1 Cum.Bull. 18 (holding that a Lawyer Trust Account Fund created by a state supreme court as a vehicle for channeling to “public purposes” income earned on client funds held by attorneys in a fiduciary capacity “is not subject to federal income tax since the Fund is an integral part of the state”).
Each of these rulings was based on an understanding — doubtless an informed understanding — of the intent of Congress. The rulings are consistent with a principle of statutory construction that was suggested by Justice Rutledge when the United States Supreme Court abandoned the constitutionally-based governmental function/proprietary function test in 1946. Justice Rutledge urged that the Court apply a rule of construction “requir[ing] that before a federal tax can be applied to activities carried on directly by the States [as opposed, presumably, to activities carried on by the states through private instrumentalities], the intention of Congress to tax them should be stated expressly and not drawn merely from general wording of the statute applicable ordinarily to private sources of revenue.” State of New York v. United States, 326 U.S. at 585, 66 S.Ct. at 315-16 (Rutledge, J., concurring). [824]*824Justice Rutledge went on to say that “I should expect that Congress would say so explicitly, were its purpose actually to include state functions, where the legal incidence of the tax falls upon the state.” Id.
A rule of construction comparable to that urged by Justice Rutledge in the tax context has more recently been applied by the Supreme Court in a variety of non-tax situations. See, for example, Atascadero State Hospital v. Scanlon, 473 U.S. 234, 242, 105 S.Ct. 3142, 3147, 87 L.Ed.2d 171 (1985), where, in holding that the Rehabilitation Act of 1973 did not represent a Congressional abrogation of the immunity from suit enjoyed by states under the Eleventh Amendment, the Court declared that Congress must express any such intent “unequivocally.” See also Will v. Michigan Dept. of State Police, 491 U.S. 58, 65, 109 S.Ct. 2304, 2309, 105 L.Ed.2d 45 (1989) (“The language of [42 U.S.C.] § 1983 ... falls far short of satisfying the ordinary rule of statutory construction that if Congress intends to alter the ‘usual constitutional balance between the States and the Federal Government,’ it must make its intention to do so ‘unmistakenly clear in the language of the statute’ ” (quoting Atascadero, 473 U.S. at 242, 105 S.Ct. at 3147)); Gregory v. Ashcroft, 501 U.S. 452, 461, 111 S.Ct. 2395, 2401, 115 L.Ed.2d 410 (1991) (citing Will’s “plain statement rule” in holding that the federal Age Discrimination in Employment Act does not apply to state judges).
Section 511(a) of the Internal Revenue Code, 26 U.S.C. § 511(a), furnishes an interesting example of a “plain statement” on the taxability of a certain type of income realized by public colleges and universities. Private colleges and other eleemosynary institutions have long been taxed on their “unrelated business taxable income.” Section 511(a)(2)(B) now makes it very clear that the tax on such unrelated business income applies in the case of state colleges and universities as well. The tax applies, this section says,
“in the case of any college or university which is an agency or instrumentality of any government or any political subdivision thereof, or which is owned or operated by a government or any political subdivision thereof, or by any agency or instrumentality of one or more governments or political subdivisions. Such tax shall also apply in the case of any corporation wholly owned by one or more such colleges or universities.”
Congress has never adopted a “plain statement” such as this with regard to the investment income, as opposed to the unrelated business income, of state colleges and universities or other public instrumentalities of the state. If Congress wants to tax the investment income of public bodies, it knows how to make the kind of “plain statement” necessary to impose such a tax.
The United States does not deny that the “plain statement rule” applies in the tax field. It argues, however, that the “rule obviously does not apply where, as here, the activities are carried on by an entity that is not a political subdivision of a state or otherwise an integral part thereof.” This argument turns, of course, on the proposition that the education trust is not a political subdivision or otherwise an integral part of the State of Michigan. We are not persuaded, on the record before us, that this proposition is correct.
For guidance in determining whether an entity is part of a state for federal tax purposes, we look first to a pair of Second Circuit decisions involving § 103 of the Internal Revenue Code, 26 U.S.C. § 103. Subject to exceptions not relevant here, that section excludes from taxable income the interest on “any State or local bond,” such a bond being defined as “an obligation of a State or political subdivision thereof.” In Commissioner v. Shamberg’s Estate, 144 F.2d 998 (2d Cir.1944), cert. denied, 323 U.S. 792, 65 S.Ct. 433, 89 L.Ed. 631 (1945), and Commissioner v. White’s Estate, 144 F.2d 1019 (2d Cir.1944), cert. denied, 323 U.S. 792, 65 S.Ct. 433, 89 L.Ed. 632 (1945), the Second Circuit addressed the question whether the Port of New York Authority and the Triborough Bridge Authority were “political subdivisions” for § 103 purposes. The court’s answer, delivered in opinions written by Judge Augustus Hand, was “yes.”
[825]*825The pertinent treasury department regulations, as quoted in Shamberg, 144 F.2d at 999-1000, said that “[t]he term ‘political subdivision’ ... denotes any division of the State or territory which is a municipal corporation, or to which has been delegated the right to exercise part of the sovereign powers of the State or Territory.” The Port of New York Authority — “a body politic and corporate” through which the states of New York and New Jersey built and operated the George Washington Bridge, the Holland and Lincoln Tunnels, and other projects “operated in the interest of the public without profit to private persons,” id. at 1000 — was held to fit this definition notwithstanding that the authority lacked the power to impose taxes, had no power to pledge the credit of either state, and was not subject to the debt limiting provisions of the state constitutions.6
Judge Hand found support for this holding in the test laid down in an opinion given by Attorney General MeReynolds soon after § 103 was first adopted:
“The term ‘political subdivision’ is broad and comprehensive and denotes any division of the State made by the proper authorities thereof, acting within their constitutional powers, for the purpose of carrying out a portion of those functions of the State which by long usage and inherent necessities of government have always been regarded as public.” 30 Op.Atty.Gen. 252 (1914), as quoted at 144 F.2d at 1004.
“[T]he real criterion adopted by the Attorney General,” Judge Hand observed, “seems to have been whether the activities of the subdivision were for a public purpose.” Shamberg, 144 F.2d at 1004.
Applying this criterion to the facts before us, we think it obvious that encouraging higher education by helping provide the means for attendance at Michigan’s public colleges and universities — the basic function for which the education trust was established by the Michigan legislature — is at least as much a “public function” as building and operating bridges and tunnels. See Brown v. Bd. of Education, 347 U.S. 483, 493, 74 S.Ct. 686, 691, 98 L.Ed. 873 (1954), where the Supreme Court said that “education is perhaps the most important function of state and local governments.” The contractual obligations of the Michigan Education Trust are no less the obligations of a “political subdivision,” in our view, than the obligations of the Port of New York Authority or the Triborough Bridge Authority.
As we have seen, the treasury regulations quoted by Judge Hand in Shamberg defined a “political subdivision” as any division of the state which was either a municipal corporation or to which the right to exercise a part of the state’s sovereign power had been delegated. The latter part of the definition made the court’s position “still clearer,” Judge Hand wrote, because the Port of New York Authority was a subdivision “to which has been delegated the right to exercise part of the sovereign power of the State.... ” Id. at 1005. The Triborough Bridge Authority was likewise “a subdivision of state government empowered to exercise governmental functions on behalf of the City of New York....” White, 144 F.2d at 1020.
In the case at bar, similarly, the education trust is a public agency explicitly authorized to exercise contracting powers “on behalf of the state” for a purpose that the Michigan legislature has declared “is necessary and desirable for the public health, safety, and welfare.” The education trust has thus been empowered to exercise governmental functions on behalf of the State of Michigan, it seems to us, just as Judge Hand said the Triborough Bridge Authority had been empowered to do on behalf of the City of New York. And the education trust would qualify as a “political subdivision” under the regulations in any event, we believe, since, as “a [826]*826public body corporate and politic,” it is in a broad sense a “municipal corporation.”
The same cannot be said of Temple University, a state-related entity which the Third Circuit has held not to be a “political subdivision” for § 103 purposes. See Philadelphia National Bank v. United States, 666 F.2d 834 (3d Cir.1981), cert. denied, 457 U.S. 1105, 102 S.Ct. 2904, 73 L.Ed.2d 1314 (1982). Temple was founded in the 19th Century as a private educational institution, and it was reorganized under a 1965 Pennsylvania statute that gave slightly under 40 percent of the seats on the institution’s board of trustees to designated public officials and appointees of the governor and leaders of the legislature. At the time of the reorganization, the university started receiving greater financial support from the Commonwealth than it had in the past. The legislature was empowered to set tuition schedules if it chose to make adequate appropriations, but the board of trustees continued to be responsible for the university’s affairs otherwise. The Supreme Court of Pennsylvania held that the school was not a state “agency,” and the United States successfully argued before the Third Circuit that “Temple is a private, non-profit corporation, governed by a privately controlled Board of Trustees, and has not been delegated sovereign power.” Id. at 837.
In holding that the university was not a political subdivision, the Third Circuit distinguished Shamberg and White on a number of grounds, some of which represent points on which the port and bridge authorities described in those cases differ from the education trust with which we are concerned here. The fact remains, however, that the education trust is a purely public body, like the bridge and port authorities, while Temple University is not. The Philadelphia National Bank decision fails to persuade us that the education trust is not a political subdivision.
The Third Circuit’s decision in Philadelphia National Bank is to be contrasted with that of the Second Circuit in Rose v. Long Island Railroad Pension Plan, 828 F.2d 910 (2d Cir.1987), cert. denied, 485 U.S. 936, 108 S.Ct. 1112, 99 L.Ed.2d 273 (1988), an ERISA case where the court relied heavily on income tax precedents. At issue in Rose was the status of a railroad company that had once been privately owned, but that had been acquired by New York State’s Metropolitan Transportation Authority. (The transportation authority ultimately converted the railroad into a public benefit corporation under New York law.) The Second Circuit had to decide whether the railroad was a “political subdivision [of the state or an] agency or instrumentality of [the state or a political subdivision thereof]” within the meaning of 29 U.S.C. § 1002(32). The court answered this question in the affirmative, and held that the railroad’s pension plan was exempt from compliance with Title I of ERISA as a “governmental plan.” (Emphasis supplied.)
The statutory language on which Rose turned is identical to that contained in § 414(d) of the Internal Revenue Code, 26 U.S.C. § 414(d):
“[T]he term ‘governmental plan’ means a plan established and maintained for its employees by the Government of the United States, by the government of any State or political subdivision thereof, or by any agency or instrumentality of any of the foregoing.”
Whether a particular entity is an agency or instrumentality of a state or political subdivision for purposes of § 414(d), as the Rose court observed at 828 F.2d at 918, has long been determined by the Internal Revenue Service under Rev.Rul. 57-128, 1957-1 Cum. Bull. 311. This revenue ruling lists six factors to be considered:
“In cases involving the status of an organization as an instrumentality of one or more states or political subdivisions, the following factors are taken into consideration: (1) whether it is used for a governmental purpose and performs a governmental function; (2) whether performance of its function is on behalf of one or more states or political subdivisions; (3) whether there are any private interests involved, or whether the states or political subdivisions involved have the powers and interests of an owner; (4) whether control and supervision of the organization is vested in public authority or authorities; (5) if express or implied statutory or other authority is necessary for the creation and/or use of such [827]*827an instrumentality, and whether such authority exists; and (6) the degree of financial autonomy and the source of its operating expenses.”
The Bose court found that the state-owned railroad satisfied all six of the IRS criteria. See 828 F.2d at 918.
The reasoning employed by the Second Circuit in Rose suggests that the Michigan Education Trust satisfies at least five of the criteria. (1) Like the state-owned railroad, the education trust is used for what the state legislature has determined to be a “governmental purpose.” (2) Like the railroad, the education trust performs this function on behalf of the state. (3) Like the railroad, the education trust is solely a governmental entity; no private ownership interests are involved. (4) Like the railroad, the education trust is controlled by public appointees. (5) The functions performed by the railroad were delegated to it by the Metropolitan Transportation Authority, while the functions performed by the education trust are carried out pursuant to direct statutory authorization. The education trust would not even exist, of course, but for the enactment of the statute creating it.
With regard to the sixth criterion, financial autonomy, the appellant in Rose stressed the fact that although the railroad had received large operating subsidies from the state ever since the takeover, the state was not legally obligated to fund the railroad. The court acknowledged that this was true, but observed that “[the appellant’s] argument ignores the fact that many governmental services are funded in the same manner.” Id.
Whether Michigan’s education trust will ultimately be able to continue operating without significant appropriations from the legislature remains to be seen. Michigan obviously hopes that such appropriations will never be necessary — and as in the case of the publicly-owned railroad and many similar governmental instrumentalities, there is no legal requirement that any operating deficits be covered by appropriations from the general funds of the state. If the education trust should ever find itself unable to fulfill the contractual commitments made by it on behalf of the state, however, there would undoubtedly be enormous pressure on the legislature to supply the necessary funds. This may not be enough to satisfy the sixth criterion, but viewing the six factors as a whole it seems to us that on balance they militate in favor of a conclusion comparable to that reached by the Second Circuit in Rose.
The short answer to all of this, the United States suggests, is to be found in the last two sentences of footnote 2 in United States v. Maryland Savings-Share Insurance Corporation, 400 U.S. 4, 7, 91 S.Ct. 16, 18, 27 L.Ed.2d 4 (1970) (per curiam). There the Supreme Court endorsed a lower court’s conclusion that a nonprofit mutual insurance corporation chartered to insure savings and loan accounts was not exempt from federal taxation as a state instrumentality. The Maryland Savings-Share case involved a private corporation, however, as we shall see, and not a public body; accordingly, we do not consider the case controlling here.
The Maryland Savings-Share Insurance Corporation was chartered in 1962 for the purpose of insuring the accounts of depositors in private savings and loan associations that were members of the corporation. Although not chartered under the state’s general corporation law, the corporation possessed all the powers conferred on corporations by that law. Art. 23, § 161MM, Ann. Code of Md. The corporation was not given any power to make contracts on behalf of the state. The first annual meeting of the corporation could not be held until a minimum of twenty-five savings and loan associations had become corporation members, and at that meeting the savings and loan associations were to elect eight of the eleven members of the corporation’s board of directors. Art. 23, § 16100, Ann.Code of Md. The governor of the state was to appoint the remaining three members of the board. Id. Public appointees thus held less than 30 percent of the seats on the insurance company’s board, an even smaller percentage of public appointees than Temple University had. (See Philadelphia National Bank v. United States, 666 F.2d at 836, explaining that Temple’s board of trustees had fifteen public members and twenty-four private members.)
[828]*828There was a time when all nonprofit mutual companies organized to insure accounts in member savings and loan associations were statutorily exempt from federal income taxes, but the law was eventually changed to exempt such companies only if they had been organized before September 1, 1957. 26 U.S.C. § 501(c)(14)(B). Maryland Savings-Share Insurance Corporation subsequently brought a tax refund action in which it challenged the cutoff date as a denial of due process; § 501(c)(14)(B) was arbitrary and unconstitutional, the corporation contended, because the section “exempt[ed] essentially identical corporations from taxation....” Maryland Savings-Share Insurance Corporation v. United States, 308 F.Supp. 761, 764 (D.Md.1970). The corporation also contended that its income was exempt from taxation under 26 U.S.C. § 115(a)(1) and under the intergovernmental tax immunity doctrine. Id.
The district court rejected the latter contentions, concluding among other things that the tax on the corporation imposed no burden on the State of Maryland. The district court accepted the argument that the cutoff date was arbitrary and unconstitutional, however, and a refund of taxes was granted on that basis. Id. at 768-72. On direct appeal, the United States Supreme Court reversed the judgment of the district court.
The Supreme Court’s relatively short per curiam opinion was devoted almost entirely to the due process question. It is significant for our purposes, however, that in its statement of the facts relevant to the due process issue the Supreme Court expressly recognized that the pre-1957 insurance companies with which Maryland .Savings-Share was comparing itself were “private insurers.” United States v. Maryland Savings-Share Insurance Corporation, 400 U.S. at 5, 91 S.Ct. at 17. We infer that the Court viewed Maryland Savings-Share as a private insurer too, and this inference is strengthened by the two sentences of footnote 2 in which the Court disposed of the public instrumentality issue:
“We also find unpersuasive MSSIC’s remaining argument that it is an instrumentality of the State and hence entitled to exemption from federal taxation under the doctrine of intergovernmental immunity and under § 115(a)(1) of the Code, 26 U.S.C. § 115(a)(1). The District Court properly rejected this argument.” Id. at 7 n. 2, 91 S.Ct. at 17 n. 2.
The fact that a private insurer such as Maryland Savings-Share Insurance Corporation is not entitled to tax exemption as a public instrumentality hardly means that a public body such as the Michigan Education Trust is not entitled to exemption. Unlike the insurance corporation, the education trust is clearly a public instrumentality. Unlike the insurance corporation, the education trust has a board appointed entirely by the governor of the state. And unlike the insurance corporation, the education trust makes its contracts on behalf of the state — as the Michigan legislature expressly provided in the governing statute not once, but twice. See M.C.L.A. § 390.1426 and M.C.L.A. § 390.1431.
The education trust is not an integral part of the State of Michigan, the United States argues, both because the trust’s corporate form of organization makes it “functionally independent” of the state and because the source and earmarking of its funds make it “fiscally independent.” Neither branch of the argument is persuasive.
It is “immaterial,” to borrow an adjective used by Judge Hand in White’s Estate, 144 F.2d at 1021, that the Michigan legislature decided to create a public quasi corporation to receive and invest advance tuition payments instead of assigning this function to a traditional executive department not organized in corporate or quasi corporate form. The point can be illustrated, perhaps, with an example from the federal level. This country’s postal service used to be operated by a traditional executive department; since the early 1970s, however, it has been operated by an “independent establishment,” the United States Postal Service, organized along the lines of a government corporation. See 39 U.S.C. §§ 201 et seq. No one would ever have imagined that the income of the old Post Office Department was subject to taxation by either the United States or by individual states — and to sup[829]*829pose that the income of the new Postal Service is now subject to taxation merely because the Postal Service is “functionally independent” would be absurd. The Postal Service is as much an integral part of the United States as the Post Office Department was.
It is likewise immaterial that the funds of the education trust, like the funds of many public corporations, authorities, and similar establishments, come primarily from persons to whom the entity provides a service — and it is immaterial that such funds are earmarked for the benefit of those who receive the service. If the funds of the Postal Service come primarily from persons who buy stamps, the funds of the Tennessee Valley Authority from those who purchase power from that agency, and the funds of the Port of New York Authority from users of the authority’s bridges and tunnels, it does not mean that the Postal Service, the Tennessee Valley Authority, and the Port of New York Authority are anything other than governmental in character. Neither is the governmental character of these agencies compromised in any way by the fact that the agencies’ funds are earmarked — like highway trust funds and countless other restricted accounts of governmental bodies — for use in performing the functions that the agencies were created by law to perform.
It is true that the particular individuals who attend public colleges and universities in Michigan under the state’s prepaid tuition program benefit directly from the program, while the rest of the citizenry benefits only indirectly. But much the same thing can be said of most government benefit programs, including the state student loan programs through which many students “post-pay” their tuition. Suppose the State of Michigan were to create a public quasi corporation to manage a revolving student loan fund for disadvantaged youths. If the investment income of such a body would not be held subject to taxation under existing law — and we are confident that it would not be, regardless of the body’s “functional independence” and regardless of the earmarking of its assets — it is hard to see how the investment income of the education trust could be considered taxable.
Or suppose that the State of Michigan created a public quasi corporation to hold and invest state employees’ pension funds. The only direct beneficiaries would be the employees themselves, and the agency, by hypothesis, would be functionally and fiscally independent of the general government. The notion that the pension agency would be treated as anything other than an integral part of the state strikes us as untenable— and the notion that the Michigan Education Trust is not an integral part of the State of Michigan is equally untenable, in our opinion. The education trust is an integral part of the state, and its investment income is not currently subject to taxation under § 11(a) of the Internal Revenue Code.
The foregoing analysis makes it unnecessary for us to reach the remaining issues raised on appeal, including the question whether the “very old and somewhat cryptic language” of 26 U.S.C. § 115 creates an exclusion for the education trust’s income 7 and the question whether the trust is a charitable, educational, or social welfare organization exempt from taxation by reason of 26 U.S.C. §§ 501(c)(3) or 501(c)(4).
The judgment of the district court is REVERSED, and the case is REMANDED with instructions to grant the refund.