Voluntary contributions to a retirement annuity fund cannot be included in the calculation of loss of future earnings under section 17(4) of the Road Accident Fund Act. There is a material distinction between employer pension fund contributions and retirement annuity contributions: the former are non-voluntary, arise from employment contracts, and form part of employment benefits, while the latter are voluntary and constitute personal investments rather than employment benefits. The exclusion of retirement annuity contributions from loss of future earnings calculations does not amount to unlawful discrimination because pension fund contributions and retirement annuity contributions are not similarly situated due to their fundamentally different nature.