• “(6) Proportionate share is the local authority's proportionate share of the other half of the costs. The authority's proportionate share is calculated by—

  • “(a) determining the total of the operating expenditures of authorities to which this subclause applies; and

  • “(b) determining the proportion that the operating expenditure of the authority bears to the amount in paragraph (a); and

  • “(c) applying the proportion to the half of the costs.

• “(7) Subclause (6) does not apply to a local authority whose population is less than 1 000 persons. An authority's population is its population at the most recent of the following dates:

  • “(a) the date of the last census of population and dwellings taken by the Government Statistician for which results have been published:

  • “(b) the date on which the authority was constituted, if an assessment by the Government Statistician of the population at that date exists:

  • “(c) the date of the last alteration of the authority's boundaries, if an assessment by the Government Statistician of the population at that date exists:

  • “(d) a date other than a date described in paragraph (b) or (c), if an assessment by the Government Statistician of the population at that date exists.

• “(8) For the purposes of subclause (6), the operating expenditure of a local authority is,—

  • “(a) for an authority that has the same boundaries as at the commencement of the previous financial year, the amount the Government Statistician publishes as the operating expenditure of the authority for that financial year:

  • “(b) for any other authority, the amount that the Government Statistician determines as being a reasonably attributable sum of the operating expenditures in the previous financial year of those local authorities whose district or regions now constitute the district or region of the authority.”