Effective January 3, 1977, and until otherwise provided by law, the rate of pay for each of the six positions of minority employee authorized by the Legislative Pay Act of 1929 and referred to in House Resolution 441 of the Ninety-first Congress shall be a per annum gross rate equal to the annual rate of basic pay of level IV of the Executive Schedule of section 5315 of title 5, unless a lower rate is established by the Minority Leader.