Alternative metrics in scientometrics: A meta-analysis of research into   three altmetrics
  Alternative metrics are currently one of the most popular research topics in scientometric research. This paper provides an overview of research into three of the most important altmetrics: microblogging (Twitter), online reference managers (Mendeley and CiteULike) and blogging. The literature is discussed in relation to the possible use of altmetrics in research evaluation. Since the research was particularly interested in the correlation between altmetrics counts and citation counts, this overview focuses particularly on this correlation. For each altmetric, a meta-analysis is calculated for its correlation with traditional citation counts. As the results of the meta-analyses show, the correlation with traditional citations for micro-blogging counts is negligible (pooled r=0.003), for blog counts it is small (pooled r=0.12) and for bookmark counts from online reference managers, medium to large (CiteULike pooled r=0.23; Mendeley pooled r=0.51). 
Lutz Bornmann
cs.DL physics.soc-ph