Series Participation Visualizer is a userscript that adds an interactive graph to the Home page of every official series which shows the participation stats (meaning: the amount of drivers and the strength of field, did it split, etc) for each race. This allows you to very quickly see when a series is popular and when SOF races are.
You can also see the Average participation per week day, averaged over the current season so far.
Simply visit the series home page by clicking the series from the Series overview or via the 'Home' link under the series dropdown in the Race Now panel.
Click the 'Averaged' button to show the average per week day, or click the 'Season' button to show the entire season so far to view week-by-week participation.
You can zoom and move the graph so it shows stats for one day, one week, the entire season, or anything in between. Hover over a bar to see a more detailed view. You can even click the bar to go to the results of that session!
For multi-class series, the participation is broken down in number of drivers per class both visually and in the mouse-over tooltip so you can quickly see how many drivers of your class were racing.
The easiest way to install is by using TamperMonkey (chrome) or GreaseMonkey (Firefox):
Then, install the script by visiting this link and clicking Install: