Mainstream developmental mentoring has a major impact on retention. Case studies from well-managed corporate programmes consistently show that mentees are at least a third more likely to remain with the organisation over a given period than control groups. And there are much higher outlier results; the most dramatic being a programme some years ago at GlaxoSmithKline that resulted in just a 2% loss of staff who were mentored, compared to a 26% loss of staff who were not mentored.

Explanations for why mentoring supports retention so well usually tend to revolve around mentees. Firstly, they feel more valued by the organisation. (It is interesting that there is a strong, positive correlation between mentoring relationship quality and the perception by both mentor and mentee that the organisation is supportive of the relationship.) Secondly, they find it easier to map out a more purposeful career direction within the organisation. Talented people so often leave because they can't see clearly the opportunities open to them. The mentor provides a much wider perspective that helps the mentees create an inspiring career narrative inside the organisation.

Thirdly, mentors often help mentees rehearse and prepare for critical conversations, such as convincing their boss to allow them to take on greater responsibilities. Through learning conversations and role modelling of their mentors, mentees develop early in their careers the skills to work constructively with conflict, rather than run away from it. (People who frequently move employers may never develop this vital leadership skill.) Fourthly, there are numerous accounts of mentees who have grown frustrated with being too long in one role, changing their minds completely when their mentor helps them understand the learning potential that remains by staying a bit longer where they are.

Less obvious, but equally important, are factors relating to the mentor. Talent isn't always recognised when it doesn't conform to established stereotypes. Mentors can make the organisation more aware of this talent and help talented individuals align their own development with future organisational needs. There are a number of reported cases where feedback from mentors has changed people policy in ways that aid retention of such groups as specialists, women and racial minorities.

“It is hard to believe that any organisation serious about retention is not investing in mentoring”

The openness of the mentoring conversation, compared with conversations between direct report and boss, makes it much more likely that trigger points for quitting (such as the psychological change that makes new fathers compare their career progress with social peers) can be dealt with in ways that include thinking about achieving changed aspirations without moving employer. In mid-career, mentors also help mentees through the difficult transitions of midlife crisis and aligning personal values with the realities of leadership.

Some applications of mentoring have been designed with retention in mind. Internally resourced maternity mentoring, for example, proves far more effective than externally resourced maternity coaching, because it is based on understanding the realities of the organisational culture. Mentored mums are more likely to return, get up to speed faster and stay longer.

The other side of mentoring's effectiveness lies in the deeper understanding that the organisation gains of its talent. The breadth of the mentoring conversation provides insight into people and unrealised potential in their current roles.

In short, it is hard to believe that any organisation serious about retention is not investing in mentoring.