From a fragment of a discussion on Quora – What’s the single most valuable lesson you’ve learned in your professional life? (there are over 228 answers). This one from Edmond Lau was one of my favorites. There are many good points in this answer. Here is one, I really like:
Mentoring new hires. Mentoring (and really managing) is an extremely high-leverage activity. Over the course of a year, an employee will spend somewhere between 1880 to 2820 hours working (assuming 47 work-weeks and somewhere between 40-60 hours per week working). Spending 1 hour every day for a month (20 hours) mentoring or training a new hire may seem like a lot of time, but it represents only about 1% of the total time the new hire will spend working his/her first year and yet can have a significant influence over the productivity and effectiveness on the other 99% of those hours..