Reliability and accuracy of altmetric providers: a comparison among Altmetric.com, PlumX and Crossref Event Data

The aim of this study is to measure differences between three relevant altmetric providers: Altmetric.com, PlumX and Crossref Event Data (CED). More than 67,000 research papers, initially extracted from PlumX, were searched in Altmetric.com and CED to compare their counts. Differences between services were analyzed regarding the number of documents with an altmetric event and the counting differences in each metric. Results show that Altmetric.com is the provider with the best coverage of blog posts, news and tweets; while PlumX better collects Mendeley readers; and CED is the site that extracts more Wikipedia citations. The study concludes that there are important counting differences due to technical errors and extracting criteria. The article recommends the use of specific services for the analysis of particular metrics. While, it should be mandatory to employ the combination of several providers, if we want to perform an overall analysis.