Traditionally, bibliometrics have been used to evaluate the usage and impact of research, but have usually been focused on journal-level metrics such as the impact factor or researcher-level metrics such as the h-index.[1] Article-level metrics, on the other hand, may demonstrate the impact of an individual article. This is related to, but distinct from, altmetrics.[2]
Starting in March 2009, the Public Library of Science introduced article-level metrics for all articles.[3]
The open access publisher PLOS provides article level metrics for all of its journals[4] including downloads, citations, and altmetrics.[5] In March 2014 it was announced that COUNTER statistics, which measure usage of online scholarly resources, are now available at the article level.[6]
