One easy way to track this is tell every employee that each month they get 3 upvotes and 3 downvotes. The votes are anonymous. (If you have less than 20 employees, then maybe just 1 upvote and 1 downvote.) They vote for their co-workers.

You'll see patterns in the upvotes and downvotes. The upvotes might signal "This person helped me a lot." The downvotes can catch interpersonal problems that might otherwise be hidden from you. For instance, someone on your team might be guilty of sexual harassment, but they are clever about hiding it from you. Your only clue will be that, say for instance, all the women keep downvoting that person.