The best metric to assure compliance with the policy of providing security awareness training to all new employees is the percentage of new hires that have completed the training, as this directly measures the extent to which the policy is implemented and enforced. The number of new hires who have violated enterprise security policies, the number of reported incidents by new hires, and the percentage of new hires who report incidents are not directly related to the policy, as they may depend on other factors such as the nature and frequency of threats, the effectiveness of security controls, and the reporting culture of the organization.
References: CISA Review Manual (Digital Version), Chapter 5, Section 5.7