ARTICLE 13. The two groups of shareholders as defined in article 6, paragraph (2), sub-paragraphs (a) and (b), shall contribute equally to the fulfillment of the Company's purpose. The criteria for determining whether such contributions are to be regarded as equal shall be established by agreement between the two groups of shareholders. In establishing such criteria, account shall be taken of price and wage rates in the two States and of all other factors relevant to an evaluation of the contributions.