eliminated benefits, rights, or features to a closed class of participants, or (ii) such section 401(o)(1)(B)(iii) or section 401(a)(26), the plan was amended before the date of the enactment of this Act to cease all benefit accruals, and is further amended after such date of enactment to provide benefit accruals to a closed class of participants. Any such section shall only apply if the plan otherwise meets the requirements of such section and in applying such section, the date the class of participants is closed shall be the effective date of the later amendment. 203. Study of appropriate PBGC premiums (a) In general The Pension Benefit Guaranty Corporation (hereafter in this section referred to as the Corporation ) shall enter into a contract with an appropriate agency or organization to conduct an independent study of the Corporation’s Single Employer Pension Insurance Modeling System. (b) Selection of independent organization The appropriate agency or organization referred to in subsection (a) shall be selected by the Board of Directors of the Corporation. Such agency or organization shall be the Social Security Administration or any other agency or organization that such Board determines is independent from the Corporation and has the expertise to conduct the study described in this section. (c) Study The independent study referred to in subsection (a) shall begin not later than 6 months after the date of the enactment of this Act and shall— (1) examine the current structure and level of premiums required to be paid by single employer plans (including fixed, variable and termination premiums) to the Corporation to evaluate whether such premiums are sufficient for the Corporation to pay the benefits guaranteed by the Corporation, (2) evaluate whether there are alternative structures and levels of premiums that would better account for the risks posed by various categories of single employer plans, including on the basis of— (A) industry, ownership structure, or size of the plan sponsor, (B) plan funded