The depth and breadth of Google Scholar: An empirical study

The introduction of Google Scholar in November 2004 was accompanied by fanfare, skepticism, and numerous questions about the scope and coverage of this database. Nearly one year after its inception, many of these questions remain unanswered. This study compares the contents of 47 different databases with that of Google Scholar. Included in this investigation are tests for Google Scholar publication date and publication language bias, as well as a study of upload frequency. Tests show Google Scholar's current strengths to be coverage of science and medical databases, open access databases, and single publisher databases. Current weaknesses include lack of coverage of social science and humanities databases and an English language bias.