In the case of Firefox, statistics on web browser usage are collected by several sources (not least Google, who want to see whether the money they pay for search bar placement is well spent), so there exists a quantitative way to test how well the project is serving its audience.
In your analysis you forgot about one important audience: those who do not use the program at all yet. (When starting a new project everyone falls into this category, and even for Firefox the majority of the world's population does not use it.)
Posted Dec 2, 2012 10:04 UTC (Sun) by man_ls (subscriber, #15091)
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Statistics on browser usage are not exactly quality feedback. Consider this scenario: Firefox 85 comes out with 10 new end-user features, 5 new enterprise features and with a new advertising campaign. Usage goes down 0.1%. Who is to blame? What did they do wrong? Is the world moving on? Are there any features in the competition which Firefox did not implement? Did MS or Google come up with a (possibly dirty) strategy to steal users? In the absence of detailed feedback it is impossible to know.
Statistics are good only to check whether things go broadly according to plan or there is a need to dig deeper into why.