Sheryl Sandberg, then COO of Facebook, delivered the commencement address at Barnard College in 2011, two years before her book 'Lean In' would make these ideas famous worldwide. Her most powerful observation was about how women leave the workforce not through one dramatic decision but through a series of small, almost imperceptible choices made years in advance. Sandberg described women in the last year of medical school choosing a less interesting specialty because they might want 'balance' someday, or women in the fifth year of a law firm deciding not to pursue partner because they know they'll eventually want children — even though they don't yet have relationships, let alone families. These women start 'quietly leaning back' without even realizing it, and when they eventually do have to make a choice, they find they've already given away their options. The solution, Sandberg argued, was to stay fully engaged until the actual moment of decision arrives.