Who owns CRM data, broker or agent?

Brokers own listings but who owns the contact management data, is it the broker or the agent?  My guess is that the practice is the agent takes their contact list with them when they leave, and the brokers don’t say anything, but I wonder if they could object if they wanted?  The reason the listings are the broker’s is because the agent is acting on behalf of the broker.  So, if they are working on behalf of the broker when they sign a listing, are they not also working on behalf of the broker when they get and manage new leads?   As I noted in my last post, I haven’t heard this issue addressed before in terms of MLS systems, yet I think it’s an important issue.  What is the right answer?