What performance measures or metrics do you use to determine the impact of data governance and data management activities (e.g., master data management, data cataloging, business glossary, data policies, data sharing, etc.)?

It is massive list across these different practices. If I pick data sharing as an example :
Total Subscriptions
Total Subscribers
Total jobs executed
Total bytes scanned
Daily Subscriptions
Subscribers per organization
Daily Executed Jobs
Tables' job frequency

Below is a few measure to think about...

1) Data Existence (Measure completeness of records and missing-ness by domain)

2) Accessibility (Measure number of reports pulled per month, totals users, number of new reports or views) 

2) Discoverability (Percentage of business terms in catalog or glossary) 

3) Fitness (Derive a relevancy score for each domain as pertains to your business or business processes)

4) Understandability (Validation from business users using Likert Scale)