Empirical Evidences in Citation-Based Search Engines: Is Microsoft   Academic Search dead?
  The goal of this working paper is to summarize the main empirical evidences provided by the scientific community as regards the comparison between the two main citation based academic search engines: Google Scholar and Microsoft Academic Search, paying special attention to the following issues: coverage, correlations between journal rankings, and usage of these academic search engines. Additionally, selfelaborated data is offered, which are intended to provide current evidence about the popularity of these tools on the Web, by measuring the number of rich files PDF, PPT and DOC in which these tools are mentioned, the amount of external links that both products receive, and the search queries frequency from Google Trends. The poor results obtained by MAS led us to an unexpected and unnoticed discovery: Microsoft Academic Search is outdated since 2013. Therefore, the second part of the working paper aims at advancing some data demonstrating this lack of update. For this purpose we gathered the number of total records indexed by Microsoft Academic Search since 2000. The data shows an abrupt drop in the number of documents indexed from 2,346,228 in 2010 to 8,147 in 2013 and 802 in 2014. This decrease is offered according to 15 thematic areas as well. In view of these problems it seems logical not only that Microsoft Academic Searchwas poorly used to search for articles by academics and students, who mostly use Google or Google Scholar, but virtually ignored by bibliometricians 
Enrique Orduna-Malea, Juan Manuel Ayllon, Alberto Martin-Martin,   Emilio Delgado Lopez-Cozar
cs.DL