“Leprechaun Hunting & Citogenesis § Citogenesis: How Often Do Researchers Not Read The Papers They Cite?”, 2014-06-30 (; similar):
One fertile source of leprechauns seems to be the observation that researchers do not read many of the papers that they cite in their own papers. The frequency of this can be inferred from pre-digital papers, based on bibliographic errors: if a citation has mistakes in it, such that one could not have actually looked up the paper in a library or database, and those mistakes were copied from another paper, then the authors almost certainly did not read the paper (otherwise they would have fixed the mistakes when they found them out the hard way) and simply copied the citation.
The empirically-measured spread of bibliographic errors suggest that researchers frequently do not read the papers they cite. The frequency can be further confirmed by examining citations to see when the citers makes much more serious errors by misdescribing the original paper’s findings; the frequency of such “quotation errors” is also high, showing that the errors involved in citation malpractice are substantial and not merely bibliographic.