I stopped promoting my newsletter in random places where I might get a lot of signups and started focusing on attracting people who would actually read and value what I write.
I stopped trying to write content that would appeal to everyone and started writing specifically for the people who were already engaging with my newsletters.
Here's why this number tells you everything you need to know:
If your engagement rate is going up, your content is getting better and your audience is becoming more valuable. Even if your total subscriber count stays flat.