The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer
Article 3: Calculation of control levels
For the purposes of Articles 2 and 5, each Party shall, for each group of substances in Annex A, determine its calculated levels of:
(a) Production by:
(i) multiplying its annual production of each controlled substance by the ozone depleting potential specified in respect of it in Annex A; and
(ii) adding together, for each such Group, the resulting figures;
(b) Imports and exports, respectively, by following, mutatis mutandis, the procedure set out in subparagraph (a); and
(c) Consumption by adding together its calculated levels of production and imports and subtracting its calculated level of exports as determined in accordance with subparagraphs (a) and (b). However, beginning on 1 January 1993, any export of controlled substances to non-Parties shall not be subtracted in calculating the consumption level of the exporting Party.