21.13 For the purposes of this Part and despite subsection 4(2), systemic gender discrimination in compensation shall be identified by undertaking comparisons, in terms of compensation and in terms of the value of the work performed, using the proxy method of comparison,

(a) between each key female job class in the seeking employer’s establishment and female job classes in a proxy establishment; and

(b) between the female job classes in the seeking employer’s establishment that are not key female job classes and the key female job classes in that