{"id":464,"date":"2026-01-20T15:32:54","date_gmt":"2026-01-20T15:32:54","guid":{"rendered":"https:\/\/blog.mozilla.org\/data\/?p=464"},"modified":"2026-01-20T15:38:51","modified_gmt":"2026-01-20T15:38:51","slug":"464","status":"publish","type":"post","link":"https:\/\/blog.mozilla.org\/data\/2026\/01\/20\/464\/","title":{"rendered":"This Week in Data: There\u2019s No Such Thing as a Normal Month"},"content":{"rendered":"

(\u201cThis Week in Data\u201d is a series<\/a> of blog posts that the Data Team at Mozilla is using to communicate about our work. Posts in this series could be release notes, documentation, hopes, dreams, or whatever: so long as it\u2019s about data.)<\/p>\n

At the risk of reminding you of a Nickleback song, look at this graph<\/a>:<\/p>\n

\"An<\/figure>\n

I\u2019ve erased the y-axis because the absolute values don\u2019t actually matter for this discussion, but this is basically a sparkline<\/a> plot of active users of Firefox Desktop for 2025. The line starts and ends basically at the same height but wow<\/em> does it have a lot of ups and downs between.<\/p>\n

I went looking at this shape recently while trying to estimate the costs of continuing to collect Legacy Telemetry in Firefox Desktop. We\u2019re at the point in our migration to Glean where you really ought to start removing your Legacy Telemetry probes<\/a> unless you have some ongoing analyses that depend on them. I was working out a way to get a back-of-the-envelope dollar figure to scare teams into prioritizing such removals to be conducted sooner rather than later.<\/p>\n

Our ingestion metadata (how many bytes were processed by which pieces of the pipeline) only goes back sixty days, and I was worried that basing my cost estimate on numbers from December 2025 would make them unusually low compared to \u201ca normal month\u201d.<\/p>\n

But what\u2019s \u201cnormal\u201d? Which of these months could be considered \u201cnormal\u201d by any measure? I mean:<\/p>\n