Over the course of my career, I’ve spent countless hours talking to and hearing from leaders around the world. I’ve interviewed thousands of candidates for managerial roles and tracked the performance of those I successfully hired. I led the global management appraisal practice of our own executive search firm, Egon Zehnder. And I’ve spent years with colleagues at Harvard Business School and other academic institutions researching what makes people effective in their jobs.One key lesson I’ve drawn from all this experience? The most successful leaders are the ones who continue to learn and grow, and the best way to help yourself – or your team — do that is through assignments that involve increasing complexity.Several years ago, I worked with Ken Aramaki in Egon Zehnder’s Tokyo office to compare the potential of senior Japanese executives (that is, objective assessments from our consultants about their ability to take on bigger roles and responsibilities) and their competence (that is, objective assessments of their strategic orientation, market insight, customer impact, results orientation, leadership, ability to collaborate and influence, etc.) against the average scores for those metrics from all the executives in our worldwide database. What we found was an incredible paradox. Japanese professionals had higher potential than the global average but lower competence.