Customer Online Engagement Level measures the level of engagement of customers with each other, a company or a specific brand, measured primarily by online interaction. Customer Online Engagement takes into account individual metrics such as duration of visits, frequency of visit, depth of visit, click-through rate as well as sales, downloads, recommendations, reviews, comments, etc.
This indicator will be included in my book: Key Performance Indicators - the 100 measures every manager needs to know, which contains an in-depth description of this KPI, as well as practical advice on data collection, calculations, target setting, and actual usage.