What are article-level metrics?
Article-level metrics place relevant data on each journal article to help users determine the value of that article to them and to the scientific community in general. This information provides additional context to the article and currently includes citations, online usage data, social bookmarks, comments, notes, blog posts about the article, and ratings of the article. The program began in March 2009, and in September 2009, we added usage data to the suite of metrics. Over time, we will incrementally increase and improve the data we provide.