
Which metric actually governs each business-model type.
Croll and Yoskovitz give a framework for choosing and using metrics in a startup, on the argument that most companies measure the wrong things and that the correct metric depends on the business model and on the stage.
Their organising concept is the One Metric That Matters, meaning that at any given stage a company should focus on a single number, because attention is limited and multiple targets produce no decisions. They pair this with the stage framework: empathy, in which the company establishes that a real problem exists; stickiness, in which it establishes that the product retains users; virality, in which it establishes that users bring others; revenue, in which it establishes the economics; and scale, in which it grows.
The business model chapters are the practical core. They give six models, which are ecommerce, software as a service, free mobile applications, media, user-generated content and two-sided marketplaces, and for each they specify the metrics that matter, the benchmark values a company should compare against, and the specific ways each model fails.
They also cover the distinction between vanity metrics and actionable ones, cohort analysis as the correct method for measuring retention, the requirement that a metric be comparative and understandable, and the practice of drawing a line in the sand, meaning stating in advance what number would count as success before running the experiment. The benchmark values are from around 2013 and have shifted substantially. The book is long for its content and repeats the framework. The model-specific metric lists and the benchmark discipline are what practitioners use.
Founders and product teams choosing what to measure, particularly those who need model-specific metrics rather than general advice.
Chosen by shared topics, the entries that hold them, and the people who recommended both.


