An older version of the graph gives more detail: https://web.archive.org/web/20170701044638/https://basecamp.com/ https://web.archive.org/web/20170701044638/ht

An older version of the graph gives more detail: https://web.archive.org/web/20170701044638/https://basecamp.com/ https://web.archive.org/web/20170701044638/https://basecamp.... The two upticks in account numbers were when new versions of the products where released. I honestly forget which these were, 2 and 3?