Many jobs require people to continually develop new skills. As a manager, you should be less worried with what people know and more concerned about whether they’re able to learn.
But it’s not enough to hire curious, adaptable people; you also have to reward them for learning. When your employees have increased their knowledge and their value to the company, provide them with new and challenging opportunities.
Promote people only when they’ve acquired sufficient expertise in other jobs in the organization, not just their own. Or you could give awards for individuals who organize events or activities to promote learnability in the company (running internal conferences, bringing external speakers, or circulating information that nurtures people’s curiosity).
Reward simpler habits, too, like writing a blog, sharing articles on social media, or recommending books and movies.