1. The Most Likely Cause: Article Merging/Splitting

Google Scholar's algorithm is fully automated. It constantly tries to group different versions of the same article (e.g., preprint, conference version, journal version) into one entry. Sometimes, this process breaks or reverses.

• Sudden "Un-Merging": The most common reason for a drop. Google Scholar may have previously (and correctly) merged your highly-cited journal article with its arXiv preprint. It might suddenly "un-merge" them. Now, your profile shows two separate entries: the journal version with 50 citations and the preprint with 40 citations. Your main article's count looks like it dropped, but the citations are just split.

• Correction of a Bad Merge: Less commonly, Google Scholar may have incorrectly merged a different author's highly-cited paper with yours (e.g., due to a similar name or title). The system has now identified this error and corrected it, removing the citations that were not yours to begin with.

2. The Second Most Likely Cause: Periodic Re-indexing

Google Scholar is not a real-time database like Scopus. It is a web crawler. It periodically re-crawls and re-indexes its entire database. During this process, citation counts can fluctuate significantly. Often, this is a temporary glitch that will resolve itself within a few days as the system finishes its data recalculation.

3. Other Potential Causes

• De-indexing of Citing Sources: The source of the citation (e.g., a specific conference website, a new journal) may have been removed from Google's index. This can happen if the source website went offline, was blocked, or was identified by Google as being low-quality or "predatory."

• Correction of "Ghost" Citations: The drop may come from the removal of incorrectly parsed citations. For example, a paper's reference list might have been formatted poorly, and Google's algorithm thought it was a citation to your work. A recent update may have corrected this parsing error.

• Retraction of a Citing Paper: If a paper that cited you has been retracted, it (and its citation) may eventually be removed from the index.

What You Should Do Now

Here is a step-by-step plan to diagnose and fix the issue.

1. Do Nothing for 48 Hours: Before taking any action, wait. This is very often a temporary data artifact from a re-indexing process that will self-correct.

2. Manually Check for Duplicates: This is the most important step. Go to your Google Scholar profile and carefully look for duplicate entries of your own papers.

   • Do you now see two versions of your most-cited paper?

   • If you find duplicates, check the boxes next to both articles and click the "Merge" button at the top.

   • This will combine them back into a single entry, and the citation counts will be re-added.

3. Review Your Article List: Look at your list of publications. Do you see any articles that are not yours? It's possible a "bad merge" was just corrected. If so, the drop in citations is actually an improvement in your profile's accuracy.

4. Check the "Cited By" List: Click on the citation number of the affected paper. Scan the list of citing articles. Do you notice any specific papers missing that you know used to be there? This can help you identify if a specific source was de-indexed.

In 99% of cases, the issue is either a temporary glitch that will fix itself (Step 1) or a merging problem that you can fix yourself (Step 2).

Would you like me to provide a more detailed guide on how to merge duplicate articles on your profile?