Updated July 1, 2008
Citation
Thresholds for Scientists, Countries, Institutions, and
Journals
Essential Science IndicatorsSM
rankings are based on a selection of the most cited scientists,
institutions, countries, and journals in a ten-year period. To
compensate for varying citation rates across scientific fields,
different thresholds are applied to each field. The thresholds are
set to select roughly the same proportion of entities from each
field. For scientists the top 1% of names is selected for each of
the fields. This percentage of inclusion translates into a specific
citation frequency cutoff for each field. For institutions this
percentage is also 1%, but for countries and journals 50%.
Highly Cited
Papers Thresholds
Thresholds are also set to select highly cited papers to be listed in
Essential Science Indicators. In this case different
thresholds are set for both field and year of data. Setting different
thresholds for each year period allows comparable representation for
older and younger papers for each field. For each field and time period
the top 1% of papers is selected. This
table shows the
citation count thresholds for each field and year corresponding to this
top cut. In the selection process the appropriate threshold is compared
against the cumulative citation count for each paper.
Hot Papers
Thresholds
The selection of Hot Papers in Essential Science Indicators is
similarly based on selecting the top cited papers in different fields,
but the time frame for citing and cited papers is much shorter, namely,
papers must be no more than two years old and cited within a current
two-month time period. This means that papers must have received
attention within a recent time frame. Papers are assigned to two-month
periods and thresholds are set for each period and field to select 0.1%
of papers, as shown in this
table. The
selection process compares the appropriate threshold against the
citation count of the paper in the most recent two-month period.
Also see "Methodology," for
other information on how Essential Science Indicators works.
