The Monday number: first-week retention

Total members is the number everyone puts on a slide, and it's the least useful number you have. It only goes up. It can't tell you whether the place is healthy, only that people once clicked a sign-up button.

The number I check every Monday morning is first-week retention: of the people who joined in a given week, how many came back and did something during the following week? A login on its own counts for little. A reaction, a comment, a post or joining a group all count.

Why this one

• It moves fast enough to show the effect of changes you make, usually within a couple of weeks.
• It reflects the newcomer experience, which is where most communities quietly fail.
• It's hard to fake. You can buy sign-ups; you can't easily buy a second visit.

Measuring it without a data team

Export new members by join date, along with their activity for the following seven days. A spreadsheet is fine to start with. Group by join week, count the members with at least one action and divide by the total. Later in this course we'll turn that into a small dashboard you can refresh in a minute.

Don't panic about the absolute value. A niche professional community and a big hobby forum will have very different baselines. What matters is the trend in your own numbers and what was happening in the weeks it moved.

Before the next lesson: calculate first-week retention for your last four join weeks and note one thing that was different about the best week.