When you're unsure how to improve a key performance indicator, it's best not to measure it. While metrics are a great way to focus energy on particular types of improvement, if poor ones are selected, people quickly optimize the wrong things. This can lead to a misalignment of incentives for team members and lousy signaling to investors and customers about your team's progress and priorities. In the worst case, this could force you to disclose numbers that make you look bad unnecessarily.
Satisfying your curiosity about your performance isn't reason enough to measure something. Bad numbers are demoralizing for a team that's working hard, and if these metrics stay the same because no one knows how to improve them, the resentment that can quickly get out of hand.
Don't be scared to use metrics, just be careful how you do.