With this release, we've provided you with more options and control over ranking and sorting options. You now have the ability to configure ranking and sorting options based on statistical information we gather about your content, such as most viewed, or top content for last week, for example.
As you know, Sitecore Search tracks valuable statistics about your content such as clicks, conversions, views, and searches. These valuable insights are stored as inner attributes within the rfk_stats composite attribute. Sitecore Search uses these attributes internally to generate analytic reports. With this release, we've exposed these statistical inner attributes, and made them available to configure as sorting or ranking options on your website.