When I started my career, I thought you should never say “I don’t know”; otherwise, people would think you weren’t competent. I have found much power in saying I don’t know because you open the door to others sharing their knowledge, and you as a leader learn. To get the value out of the phrase, follow it with “what do you think” or “let’s find out together” and learn from others. They’ll appreciate the opportunity to teach, and you may learn something new.