Reference income14.
For the purposes of these regulations the appropriate Minister shall determine in respect of each calendar year—
(a)
a reference income per labour unit for Great Britain and Northern Ireland respectively, which shall not exceed the average earnings of full-time workers in occupations other than agriculture;
(b)
a percentage increase in the reference income, having regard to the average annual increase during the preceding five years in the earnings of full-time workers in occupations other than agriculture after adjustment for changes in retail prices.