Impact of a reclassification on Web of Science articles on bibliometric indicators

In order to avoid the ambiguous classification of articles in multiple categories in the Web of Science and the resulting complication of bibliometric indicators, a reclassification of articles in the Web of Sciences categories was carried out according to the method of S. Milojevi\'c (2020). The higher hierarchical level from the OST classification into 11 scientific disciplines is also revised. Though in most cases articles are assigned to a subject category close to the original category, the reclassification changes the subject category of about 50% of the documents of the database. Therefore, the world distribution of disciplines and disciplinary profiles of scientific actors are modified. A sample of twenty five countries highlights the impact of the reclassification on country specialization indexes. Field-normalized indicators are also impacted. The level of changes is explored in the case of the Mean Normalized Citation Indicator (MNCS). A more in-depth analysis of the MNCS in Mathematics is carried out and reveals different strategies of countries to publish works with a mathematical background.