Cross-metric compatability and inconsistencies of altmetrics

Metrics like the number of tweets or Mendeley readers are currently discussed as an alternative to evaluate research. These alternative metrics (altmetrics) still need to be evaluated in order to fully understand their meaning, their benefits and limitations. While several preceding studies concentrate on correlations of altmetrics with classical measures like citations, this study aims at investigating metric-compatibility within altmetrics. For this purpose, 5000 journal articles from six disciplines have been analyzed regarding their metrics with the help of the aggregators PlumX and Altmetric.com. For this set, the highest numbers of events have been recognized regarding Mendeley readers, followed by Twitter and Facebook mentions. Thereby variations considering the aggregators could be observed. Intra-correlations between the metrics across one aggregator have been calculated, as well as inter-correlations for the corresponding metrics across the aggregators. For both aggregators, low to medium intra-correlations could be calculated which shows the diversity of the different metrics. Regarding inter-correlations, PlumX and Altmetric.com are highly consistent concerning Mendeley readers (\(r=0.97\)) and Wikipedia mentions (\(r=0.82\)), whereas the consistency concerning Twitter (\(r=0.49\)), blogs (\(r=0.46\)) and Reddit (\(r=0.41\)) is on a moderate level. The sources Facebook (\(r=0.29\)), Google+ (\(r=0.28\)) and News (\(r=0.11\)) show only low correlations.