As tech companies continue to struggle with diversifying their ranks, they often point to the talent pipeline as an issue. While that challenge is up for debate—especially since there are twice as many black and Hispanic computer science graduates as there are hires from those minority groups—research shows a proven way to boost diversity in the pipeline to the top. Mentoring programs make companies’ leadership significantly more diverse, according to a study reported in the Harvard Business Review. The study found that formal mentoring programs within organizations boosted minority and female representation in management on average by 9 to 24 percent. Some of the largest increases in leadership positions were among black women (18 percent), Hispanic women (23.7 percent), and Asian women (24 percent). The research only fortifies other studies that have cited mentoring as critical to retention, engagement, and a healthy talent pipeline. The National Human Services Assembly says mentoring promotes diversity by providing equal opportunity for every employee to grow professionally; DiversityInc, an organization that has been ranking the top 50 companies in the U.S. for diversity since 2001, cites mentoring as one of its key categories for diversity.

Why is Mentoring Effective at Boosting Diversity?

While many tech companies have implemented unconscious bias training and other diversity initiatives over the years, the measures haven’t moved the needle on improving diversity numbers, particularly in management. In fact, diversity training alone can actually be detrimental to diversity. Alexandra Kalev, co-author of the report “Why Diversity Programs Fail,” explained that managers don’t internalize diversity training because it’s mandatory and they feel forced to do it. It gives a sense of external control, which in turn creates resistance. Organizations that only used mandatory diversity training saw as much as a 9.2 percent decline in the number of underrepresented groups in management. But mentoring may have the ingredients of successful change because it engages managers in the goal of diversity. “Mentoring makes managers a part of the change by helping them know the workers of certain minority groups which they usually have stereotypes and biases against,” said Kalev, a professor at Tel Aviv University. “During this relationship, the mentors themselves become engaged, committed and invested in the success of their mentees. This helps them reduce their biases and learn about the representative of the minority group and makes them become champions of diversity.”

Formal Mentoring vs. Informal Mentoring

For mentoring to boost diversity, it must be a formal, structured program as opposed to an informal one. Kalev suggests that, while white males tend to find mentors through their own social networks and can benefit from an informal structure, minorities and women are less likely to get a mentor through an informal program. One reason, according to Harvard professor David Thomas’ research, may be because white male executives aren’t comfortable reaching out informally to young women and minorities. But if they are assigned a mentee in a formal program, they’re usually eager to assist. All of DiversityInc’s Top 50 diverse companies have formal mentoring programs. The organization says formal mentoring is controlled and monitored, which is vital to a successful program. According to Rene Petrin, president of Management Mentors, a successful program must have a well-defined process, specific goals, and a roadmap for mentors and protégés to follow, such as how often and for how long they’ll meet. In addition, both parties must receive training for the program to be successful.

Cross-Cultural Mentoring

So is it better to have cross-cultural mentoring, or have protégés mentored by someone of the same culture or gender? There are studies to support each. A recent study found that female engineering undergraduates who were paired with female mentors felt more motivated and self-assured than those with male mentors or no mentors at all. However, another study found that women who were mentored by senior male leaders saw increases in compensation and career progress satisfaction, particularly those who worked in male-dominated industries such as tech. Petrin thinks that many organizations don’t have enough women or minorities in leadership roles to have same-gender or same-culture mentors. “I find cross-cultural mentoring most helpful as opposed to same culture because that’s what will lead to change,” Petrin said. “If you’re just doing peer mentoring on some level, you may not be breaking the glass ceiling. So strategically you need to think about what’s your purpose, and, specifically when it comes to diversity, will it have an impact.” Kalev said that, when comparing mentoring programs to affinity programs in organizations—groups where workers of the same culture or gender in an organization gather—the latter programs are ineffective at bringing women or minorities into management. “You need to have ties to the higher-ups, not to people you share the same cultural or demographic background with, because they don’t necessarily have the power to promote you,” Kalev said. Solving the diversity problem in the tech industry isn’t something that will happen overnight, and mentoring especially needs time to build the diversity pipeline. Positions need to open, and organizations need to expand before they can fill key roles with diverse talent. Kalev said it takes about three to four years on average before an organization will see a significant difference in diversity from mentoring programs. The key, Kalev added, is measuring the progress of the program and holding the organization accountable to ensure it’s going in the right direction.