According to Fortune’s Anne Fisher,¹ the Human Resources department of Sun Microsystems analyzed 1,000 employees over five years and found: 

• Both mentors and mentees were approximately 20 percent more likely to get a raise than people who did not participate in the mentoring program.
• 25 percent of mentees and 28 percent of mentors received a raise — versus only 5 percent of managers who were not mentors.
• Employees who received mentoring were promoted FIVE times more often than people who didn’t have mentors.
• Mentors were SIX times more likely to have been promoted to a bigger job.²
  

¹ Anne Fisher, "Being a Mentor Could Boost Your Own Career," CNN Money, March 13, 2007. 

² Lisa Quast, "How Becoming a Mentor Can Boost Your Career," Forbes, October 31, 2011.