Here's the answer I came up with:

We Have 7.5% Witness Voting Engagement.

Inactive Accounts: 178,339
Active Accounts with a Voting Proxy: 652
Active Accounts with at Least One Witness Vote: 7,233
Active Accounts with No Witness Votes: 105,076

You can see more details on this post, along with the top 100 active accounts by VEST who aren't yet voting for a witness.