For the past forty-plus years, HR professionals have measured how time is spent, asserting that 70 percent of learning should happen through on-the-job experiences, 20 percent through coaching and mentoring, and 10 percent through classroom instruction.152 Companies as diverse as Gap,153 the consultancy PwC,154 and Dell155 describe their 70/20/10 development programs on their corporate websites.li But the 70/20/10 rule used by most learning professionals doesn’t work.
