; vacancies Each member shall be appointed for the duration of the Commission. Any vacancy in the Commission shall not affect its powers, and shall be filled in the manner in which the original appointment was made. (f) Hearings In carrying out its duties under this Act, the Commission is authorized to hold such hearings and take testimony with respect to matters to which it has a responsibility under this Act. The Chairperson, or any member authorized by the Chairperson, may administer oaths or affirmations to witnesses appearing before the Commission. The Commission shall hold, at minimum, not fewer than 4 hearings in a location that is outside of the metropolitan area of Washington, DC, and within the United States. (g) Compensation Members of the Commission shall serve without pay. (h) Travel expenses Each member of the Commission shall be allowed travel expenses, including per diem in lieu of subsistence, at rates authorized for employees of agencies under subchapter I of chapter 57 of title 5, United States Code, while away from their homes or regular places of business in the performance of services for the Commission. 4. Duties of the Commission (a) Study of retirement security The Commission shall— (1) conduct a comprehensive study of the state of retirement security in America, which shall include— (A) a comprehensive review of private benefit programs existing in the United States, with a particular focus on the historical movement from defined benefit to defined contribution models; (B) a comprehensive review of private retirement coverage, individual and household accounts balances, investment trends, costs and net returns, and retention and distribution during retirement; (C) a comprehensive review of societal trends, including wage growth, economic growth, unique small business challenges, serial employment, gig economy, health care costs, life expectancy, and shrinking household size, that could lead future generations to be less financially secure in retirement compared to previous generations