(1) Where the number of units of pension for which an employee is required to contribute would, but for this section, be reduced by reason of a reduction in his salary or in the prescribed amount, the employee shall, subject to subsection (2), continue to contribute for the number of units for which he was a contributor immediately before the reduction.
(2) An employee to whom subsection (1) of this section applies may, subject to section 22J, elect to reduce the number of units for which he is required to contribute to a number of units not less than the number of units ascertained in accordance with subsection (2) of section 20 as it applies in relation to him at the time of the election.