ItCó hasý beenkiến statedcho thatrằng impactIF factorsvà andphân citationtích analysistrích indẫn generalnói arechung affectedbị bytác field-dependentđộng bởi các nhân tố phụ thuộc vào từng chuyên factorsngành<ref>{{cite journal | last1 = Bornmann | first1 = L. | last2 = Daniel | first2 = H. D. | year = 2008 | title = What do citation counts measure? A review of studies on citing behavior | url = | journal = Journal of Documentation | volume = 64 | issue = 1| pages = 45–80 | doi=10.1108/00220410810844150}}</ref>, whichđiều maynày invalidatekhiến comparisonsviệc notso onlysánh acrossgiữa disciplinescác butchuyên evenngành withinkhác differentnhau fieldshoặc ofthậm researchchí ofgiữa các ngành con của cùng một chuyên ngành là không onehợp disciplinelệ.<ref>Anauati, Maria Victoria and Galiani, Sebastian and Gálvez, Ramiro H., Quantifying the Life Cycle of Scholarly Articles Across Fields of Economic Research (November 11, 2014). Available at SSRN: http://ssrn.com/abstract=2523078</ref> ThePhần percentagetrăm ofsố totaltrích citationsdẫn occurringxuất inhiện thetrong firsthai twonăm yearsđầu aftertiên publicationkể alsotừ variesngày highlybài amongbáo disciplinesđược fromxuất bản cũng có sự biến đổi lớn giữa các chuyên ngành, ví dụ từ 1–3% introng thetoán mathematicalhọc andvà physicalvật scienceslý tohọc đến 5–8% introng thecác ngành khoa học liên quan đến biologicalsinh scienceshọc.<ref>{{cite journal | author=Erjen van Nierop | title=Why Do Statistics Journals Have Low Impact Factors? | journal=Statistica Neerlandica | volume=63 | issue=1 | year=2009 | pages=52–62 | doi = 10.1111/j.1467-9574.2008.00408.x}}</ref> ThusVì impactthế, factorskhông cannotthể bedùng IF để so sánh các journal usedthuộc tocác comparechuyên journalsngành acrosskhác disciplinesnhau.
BecauseVì citationsố countslượng havetrích highlydẫn skewedphân distributionsbố lệch,<ref>{{cite journal|url=http://www.nature.com/news/beat-it-impact-factor-publishing-elite-turns-against-controversial-metric-1.20224|title=Beat it, impact factor! Publishing elite turns against controversial metric|first=Ewen|last=Callaway|date=14 July 2016|publisher=|volume=535|issue=7611|pages=210–211|accessdate=10 December 2016|doi=10.1038/nature.2016.20224|journal=Nature|pmid=27411614}}</ref> thenên meansố numberlượng oftrích citationsdẫn istrung potentiallybình misleadingcó ifthể usedgây tohiểu gaugelầm thenếu typicalnhư impactdùng ofnó để đo tác động điển hình của một bài báo riêng articleslẻ introng themột journal ratherthay thanvì theđể overallđo impacttác ofđộng tổng hợp của thechính journal itselfđó.<ref>{{cite news |title=Citation Statistics |author=Joint Committee on Quantitative Assessment of Research |publisher=International Mathematical Union |date=12 June 2008 |url=http://www.mathunion.org/fileadmin/IMU/Report/CitationStatistics.pdf |format=PDF}}</ref> ForVí exampledụ, aboutkhoảng 90% ofIF năm 2004 của journal ''[[Nature (journal)|Nature]]'''s2004chỉ impactdựa factortrên was1/4 basedsố onbài onlybáo ađược quarterxuất ofbản, itsvì publications,vậy andsố thuslượng thetrích actualdẫn numberthực ofsự citationscho formột abài singlebáo articleriêng inlẻ thetrong journal isnày introng mostđa casessố muchtrường lowerhợp thansẽ thenhỏ meanhơn numbersố oftrích dẫn trung bình của toàn bộ citationscác acrossbài articlesbáo.<ref>{{cite journal |author= |title=Not-so-deep impact |journal=Nature |volume=435 |issue=7045 |pages=1003–1004 |date=23 June 2005 |pmid=15973362 |doi=10.1038/4351003b}}</ref> FurthermoreHơn nữa, thesự strengthliên ofhệ thegiữa relationshipIF betweencủa impactjournal factorsvà oftỉ journalslệ andtrích thedẫn citationcủa ratescác ofbài thebáo bên trong journal papersđó thereinyếu hasdần beenđều steadilykể decreasingtừ sincekhi articlescác beganbài tobáo beđược availablesố digitallyhóa.<ref>{{cite journal |doi=10.1002/asi.22731 |title=The weakening relationship between the impact factor and papers' citations in the digital age |year=2012 |last1=Lozano |first1=George A. |last2=Larivière |first2=Vincent |last3=Gingras |first3=Yves |journal=Journal of the American Society for Information Science and Technology |volume=63 |issue=11 |pages=2140–2145}}</ref>
Indeed, impact factors are sometimes used to evaluate not only the journals but the papers therein, thereby devaluing papers in certain subjects.<ref>{{cite journal |author= John Bohannon |title=Hate journal impact factors? New study gives you one more reason |journal=[[Science (journal)|Science]] |volume= |issue=|pages= |year=2016 |pmid= |doi=10.1126/science.aag0643}}</ref> The [[Higher Education Funding Council for England]] was urged by the [[House of Commons of the United Kingdom|House of Commons]] [[Science and Technology Select Committee]] to remind [[Research Assessment Exercise]] panels that they are obliged to assess the quality of the content of individual articles, not the reputation of the journal in which they are published.<ref>{{cite web |url=http://www.publications.parliament.uk/pa/cm200304/cmselect/cmsctech/399/39912.htm |title=House of Commons – Science and Technology – Tenth Report |work= |accessdate=2008-07-28 |date=2004-07-07}}</ref> The effect of outliers can be seen in the case of the article "A short history of SHELX", which included this sentence: "This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination". This article received more than 6,600 citations. As a consequence, the impact factor of the journal ''[[Acta Crystallographica]] Section A'' rose from 2.051 in 2008 to 49.926 in 2009, more than ''[[Nature (journal)|Nature]]'' (at 31.434) and ''[[Science (journal)|Science]]'' (at 28.103).<ref>{{cite news | url=http://www.the-scientist.com/blog/display/57500/ |title=New impact factors yield surprises |work= The Scientist | date=21 June 2010 | last=Grant | first=Bob | accessdate= 31 March 2011}}</ref> The second-most cited article in ''Acta Crystallographica Section A'' in 2008 only had 28 citations.<ref>"[http://community.thomsonreuters.com/t5/Citation-Impact-Center/What-does-it-mean-to-be-2-in-Impact/ba-p/11386 What does it mean to be #2 in Impact?]", Thomson Reuters Community.</ref> It is also important to note that impact factor is a journal metric and should not be used to assess individual researchers or institutions.<ref name=Seglen-BMJ>{{cite journal |title=Why the impact factor of journals should not be used for evaluating research |author= Seglen, P. O. |journal=[[BMJ]] |year=1997 |volume=314 |issue=7079 |pages=498–502 |pmid=9056804 |pmc=2126010 |doi=10.1136/bmj.314.7079.497}}</ref><ref>{{Cite journal|title=EASE Statement on Inappropriate Use of Impact Factors|publisher=European Association of Science Editors|date=November 2007|accessdate=2013-04-13|url=http://www.ease.org.uk/publications/impact-factor-statement|postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}.</ref>
