Ask HN: What are good documentation metrics?

Hey HN, I'm looking for some opinions and/or experiences with tracking metrics for work other than code.

One thing I work on is a security guidelines wiki, which is read by other employees in the company. The wiki records editing metadata, like name and history, and it also tracks visiting usernames and timestamps. I've been asked to set some SMART goals for the year, and I want to include my work on the wiki.

My question: what kind of goals can someone set for technical writing like this, and how might one measure how effective this work is?