Comparison of metadata with relevance for bibliometrics between Microsoft Academic Graph and OpenAlex until 2020

OpenAlex has transferred practically all works from MAG preserving their bibliographic data publication year, volume, first and last page, DOI as well as the number of references that are important ingredients of citation analysis.

More than 90% of the MAG documents have equivalent document types in OpenAlex. Of the remaining ones, especially reclassifications to the OpenAlex document types journal-article and book-chapter seem to be valid and amount to more than 7%, so that the document type specifications have improved significantly from MAG to OpenAlex. So far, OpenAlex seems to be more suited for bibliometric analyses than MAG.

As last item of bibliometric relevant metadata, we looked at the paper-based subject classification via FoS in MAG and in OpenAlex. We found significantly more documents with a FoS assignment in OpenAlex than in MAG. On the first and second level, the FoS structure is identical resp. nearly identical, but on the deeper levels the number of available FoSs is drastically reduced to about 10%. But this would not pose a problem if using only the upper two levels for bibliometric analyses as was done by Scheidsteger, et al. However, the reclassifications might cause changes to conclusions of previous studies. The consequences of the proliferation and abundant reclassification of top-level FoSs need to be studied more in detail. Reclassifications at the deeper levels should be studied, too.

Overall, OpenAlex seems to be at least as suited for bibliometric analyses as MAG for publication years before 2021. However, this first impression needs to be checked by further detailed studies.