The publication echo: effects of retrieving literature in PubMed by year of publication.
OBJECTIVE
In PubMed search forms, the publication date refers to both the date of electronic and printed publication. This fact is documented in PubMed, but difficult to anticipate by the users and can provoke misinterpretations of search results. The Technical Note aims at systematically investing the effect (referred to as the publication echo), clarifying onset and extent of the publication echo, and comments on its impact.


METHODS
Papers with ambiguous publication dates are systematically retrieved and a trend analysis with seasonal decomposition on monthly publication data is performed.


RESULTS
First doubled search results were found for 1999, their number since then rapidly increasing. Up to 17.6% of all articles of a year are found to be published electronically and in print, which can be before or afterwards. Maximum delay between the two dates is three years, except for one singular publication, where it is five years. Publication trends are exponential and linear when considering echoed and echo-cleaned data, respectively.


CONCLUSIONS
As a conclusion, we suggest using a query formulation that unambiguously retrieves literature from PubMed by the date of publication.
Spreckelsen
Cord
C
Institut for Medical Informatics, RWTH Aachen University, Pauwelsstrasse 30, 52057 Aachen, Germany. CSpreckelsen@mi.rwth-aachen.de
Deserno
Thomas M
TM
Spitzer
Klaus
K
D000043:Abstracting and Indexing / Q000379:methods*; D001185:Artificial Intelligence; D015706:Bibliometrics; D057225:Data Mining / Q000379:methods*; D003628:Database Management Systems; D009323:Natural Language Processing; D010506:Periodicals as Topic; D039781:PubMed