Not later than
July 1, 1979, and from time to time thereafter as the Director of the Office of Personnel Management finds appropriate, the Director shall establish, by rule issued in accordance with
section 1103(b) of this title, the number of positions out of the total number of positions in the Senior Executive Service, as authorized by this section or section 413 of the Civil Service Reform Act of 1978, which are to be career reserved positions. Except as provided in paragraph (2) of this subsection, the number of positions required by this subsection to be career reserved positions shall not be less than the number of the positions then in the Senior Executive Service which, before the date of such Act, were authorized to be filled only through competitive civil service examination.