Use the Leaderboard.
Click Leaderboard in the sidebar.
Toggle between This month and Last month.
You'll see:
Active advocates — how many teammates published at least one post.
Total shares — total posts published company-wide.
Ranked list — every advocate sorted by number of published posts, with avatar and name.
Pair this with Analytics for engagement-weighted performance (likes, comments, reach) — the Leaderboard measures volume, Analytics measures impact.