The Securities and Exchange Commission green-lighted Nasdaq’s plan Friday to increase diversity among the members of its companies’ boards. Under the proposal, Nasdaq-listed companies need to meet ethnic and gender diversity targets and disclose the makeup of their boards, but it is not a full mandate. Companies can choose not to meet the diversity targets but must provide an explanation detailing their decision. A review completed before Nasdaq submitted its proposal showed more than three-quarters of the exchange operator’s companies would not have met the proposed diversity requirement.