The h and g indices What is the hindex A scientist has index h if h of hisher N p papers have at least h citations each and the other N p h papers have no more than ID: 926488
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Slide1
New ways to track scholarly productivity: The h- and g-indices
Slide2What is the h-index “A scientist has index h if h of his/her N
p
papers have at least h citations each, and the other (
N
p
−
h
) papers have no more than
h
citations each.” [Hirsch, 2005]
Shorter version
:
“an index of
h
has published
h
papers each of which has been cited by others at least
h
times.”
Slide3Who and whyCreated by Jorge E. Hirsch, a physicist at UC-San Diego, to determine theoretical physicists' relative quality.The h-index grows as citations accumulate and thus it depends on the ‘academic age’ of a researcher.
Slide4Rank=Citations
Find all your papers.
Sort them by citation count.
Scroll down until the number of citations equals the number of the paper
(in the example chart to your left, n=8).
Slide5Benefits of the h-indexIt is quantitative.It takes into account the QUANTITY of well-cited publications.The index is intended as a tool to evaluate researchers in the same stage of their careers. It is not meant as a tool for historical comparisons.
Since the
h-index
increases with time, initial work that was published early is still relevant.
Only the most highly cited articles contribute to the
h
-index.
Slide6Problems with the h-indexSelf citations are in the list. Cross field comparison is difficult.As your h
-index number increases, it becomes harder to increase it further.
The lowest citation thresholds are in the Social Sciences, Computer Science, and Multidisciplinary Sciences.
The
h
-index does not account for the number of authors of a paper.
The
h
-index gives books the same count as articles making it difficult to compare scholars in fields that are more book-oriented.
Slide7What is the g-index“Given a set of articles ranked in decreasing order of the number of citations that they received, the g-index is the (unique) largest number such that the top g articles received (together) at least g
2
citations.” [
Egghe
, 2006]
Shorter version
:
“this means that an author that produces
n
articles should have, on average,
n
citations for each of them, in order to have a
g
-index of
n
.”
Slide8Who and whyCreated by Leo Egghe, Universiteit Hasselt, Antwerpen
.
g
is expected to be a good correlation with the total number of citations an author has received, while
h
correlates with the highest number of citations which the most quoted paper brings to his author. Accordingly
g
is often greater than
h
.
In 2010, the High Impact Universities Research Performance Index (RPI) was developed, analyzing research performance for 1,000 universities and 5,000 constituent faculties.
Slide9Ranking CitationsThe g-index describes the consistency and quality of an institution faculty's research output.
Determine the g-index by ranking an individual’s publications in terms of the number of citations that each publication received. The top
g
publications should have received, in total, at least
g
^2 citations.
Slide10Benefits of the g-indexIt is quantitative.The g-index gives more weight to highly cited articles.
The total
number of documents
does
not limit the value of the
index.
The
g
-index
might be more
adequate than the
h
-index
for assessing selective
scientists
**Researchers
with selective publication strategies
are
those who do not publish a very high number of documents but who do attain a high impact
Slide11Problems with the g-indexSelf citations are in the list. Cross field comparison is difficult.
Slide12How do you find your h- and g-index?Web of ScienceHarzing’s Publish or Perish (uses Google Scholar)Google Scholar
Caveats with each db
Each database is likely to produce a different
h
for the same scholar, because of different coverage.
Google Scholar has more
citations but more chaff,
however, the smaller citation collections are more accurate as to actual published works.
Slide13Sample: Antoine BertinelliWeb of Science65 papers499 citations (no self-citations)Cites/paper= 7.15
Authors/paper: 1.80
h-index = 13
g-index = 18
Harzing Publish or Perish
68 papers [-3 lists/rosters = 65 papers total]
577 citations [includes self-citations]
Cites/year: 11.78
Cites/paper = 8.88
Authors/paper: 1.80
h-index= 14
g-index = 22
Slide14Both are necessaryThe existence of highly cited papers is heavily valued by the g-index.The
h
-index
values
a
stable profile in
the scientific
performance of scientists but penalizes selective publication
strategies.
Slide15Example: Real Person: WoS
Results found:
86
Sum of the Times Cited
[?]
:
610
Sum of Times Cited without self-citations
[?]
:
596
Citing Articles
[?]
:
590
Citing Articles without self-citations
[?]
:
579
Average Citations per Item
[?]
:
7.09
h-index
[?]
:
13
Search
on an individual’s name, mark all the citations reported in WOS, and then click on ‘Create citation report’.
Each
report is accompanied by
Two
charts, showing ‘published items in each year’
and ‘
citations in each year
’
Searches only what is captured in
WoS
.
Does not include ephemera or ghost citations (Google does).
Slide16Example: Real Person: Harzing’s Publish or Perish Query date: 2013-01-28h-index: 17
Papers: 63
g-index: 25
Citations: 776
e-index: 15.65
Years: 56
hc
-index:
4
Cites/year: 13.86
hI
-index: 8.50
Cites/paper: 12.32/7.0/1 (mean/median/mode)
hI,norm
: 12
Cites/author: 501.66
hm
-index: 12.58
Papers/author: 44.92
Authors/paper: 1.76/1.0/1 (mean/median/mode)
Searches
Google Scholar and returns results calculating the h- and g-indices for individuals and journals.
Provides
links from the cited work to the citing
works
Can be ported in Excel for further analysis
Slide17Example: Real Person:Google Scholar Universal GadgetCitations for 'SAMPLE FACULTY' : 777
Cited
Publications: 63
H-Index
: 17
However, millions of Google Scholar (GS) records have erroneous metadata, as well as inflated publication and citation counts.
GS lumps together the number of master records (created from actual publications), and the number of citation records (distinguished by the prefix: [citation]) when reporting the total hits for author name search.
It is important to check and refine the data that the gadget performs calculations on by clicking on the “view publications” link and not take the returns at face value.
Slide18Hirsch (of the h index) says:Note Qualifier is for the field of Physics, “an h index of 20 after 20 years of scientific activity
characterizes a successful scientist
”
“
an h index of 40 after 20 years of
scientific activity
characterizes outstanding scientists
likely to
be found only at the top universities or
major research laboratories”
“
an h index of 60 .. after 20
years …characterizes
truly unique
individuals”
Hirsch
JE. An index to quantify and individual’s scientific research output
. PNAS 2005;102:16569-72.