An addition to @marek's answer above.
Although the page is only available on a CM server, the output of the stats.aspx page is saved, by default, to App_Config\diagnostics\health_monitor, every 10 minutes, and kept for seven days. This is configured in App_Config\Sitecore\CMS.Core\Sitecore.Diagnostics.config.
The report will have a name like: RenderingStatistics.YYYYMMDD.FFFFFFZ.html. The output of the cache.aspx page is saved as CacheStatus.YYYYMMDD.FFFFFFZ.html. This is to allow monitoring of cache and rendering statitics on production environments.