Jefferies was acquired in 1969 by Minneapolis-based Investors Diversified Services (IDS), the second largest U.S. financial services company at the time, and resigned all its stock exchange memberships. Jefferies saw the acquisition as a means to increase the size of its institutional business with additional capital. However, because IDS did not derive at least 50 percent of its gross income from broker-dealer operations, Jefferies had to quit the New York exchange under Exchange Rule 318. In 1971, IDS and Jefferies filed an antitrust lawsuit against the exchange, seeking $6 million in damages. Jefferies and its parent company claimed that the NYSE Big Board was an illegal monopoly and that exclusion had placed the company at a competitive disadvantage. In 1973 the presiding judge informed the NYSE that he planned to rule in Jefferies' favour. Membership was opened to brokerage firms owned by other kinds of companies, so long as 80 percent of brokerage was conducted with the public. Jefferies rejoined the exchange in March 1973.