collnet expected authorrate

COLLNET 2011, September 20-23, Istanbul, Turkey

Multi-authorship and citation advantages:A mythical relationship

Bart Thijs1

Rodrigo Costas2

Wolfgang Glänzel1,3

1. ECOOM, Katholieke Universiteit Leuven, Belgium2. Leiden University, Centre for Science and

Technology Studies (CWTS), Netherlands3. Institute for Research Policy Studies, Hungarian

Academy of Sciences, Budapest, Hungary


Introduction

The study of the relation between collaboration among scientists and research output has a long tradition.

• Collaboration and production

– Price & Beaver, 1966

– Beaver & Rosen, 1979

– Braun et al. 2001

– Glänzel, 2002


Introduction• Collaboration and Citations

– Glänzel & Schubert, 2001 and Glänzel, 2001

– Schmoch & Schubert, 2008

• Collaboration patterns in specific fields or institute

– Bordons et al., 1996

– Gomez et al., 1999

– Iribarren-Maestro et al., 2009


IntroductionIn this study we investigate the relation between collaboration and citation scores.

We introduce a methodology to normalize measurements of multi-authorship and international collaboration in order to be able to investigate the relation in absence of field specific effects. These normalized measures are applied on three different levels of aggregation: journals, countries and institutes.


Data

• SCIE,SSCI from Thomson-Reuters

• Publications from the annual updates 1998-2007

• Only citable document type: Article, Letter, Proceedings Paper or Review

• 3 year citation window is used

• Leuven-Budapest classification = Journal based field/discipline classification


First observations

0

1

2

3

4

5

6

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Multi

Single

Multi authored papers have more citations than single authored papers

The difference between multi and single papers remains constant over time.


First observations

Same observations applies for countries. Papers with international collaboration have on average more citations than domestic papers.

0

1

2

3

4

5

6

7

8

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Internat.

Domestic


First observations

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Countries

Authors

Average number of citations increases with growing number of authors/countries.

Kendall t

Countries 0.15

Authors 0.21


Conclusions?Can we conclude based on these three graphs that more authors/countries leads to more citations?

More than … what?


Role of fields • Research field plays a important role on the

behaviour of scientists.

• Different fields act like different communities or even like different cultures.

0

0.1

0.2

0.3

0.4

0.5

0.6

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Authors

Countries

High rank correlation between authors and citations across 62 fields.


Central tendencyMore than ….?

…the average within the field.


Central tendency

The use of expected citation rates are very common in bibliometrics.

Analogue to these we can define an

• Expected Author Rate

• Expected Country Rate

More than ….?

…the average within the field.


DefinitionsThe Expected Author Rate for a field (EARf) is the average number of authors over all papers that are in full or partially assigned to the field within one year. Papers with multiple field assignments are fractionated and only partially counted both in numerator and denominator.

The Expected Author Rate for a journal (EARj) is the average number of authors over all papers in a journal within one year.


DefinitionsEAR and ECntrR provides us with reference standards for collaboration both for fields and for journals.

As with citations we can calculate a relative indicator that shows us whether a paper (or set of papers) has more or less authors than we might expect based on the reference standardNormalized Author Rate =

Observed Number of AuthorsExpected Author Rate


ResultsThe relation between collaboration and citation indicators will be investigated at three different levels of aggregation

• Journals

• Countries

• Institutes

Publications from 2005 to 2007

Al least 100 publications over three year period


Results: JournalsKendall’s t Average Citations

Expected Citation Rate Field 0.35

Average Number of Authors 0.35

Expected Authors Rate Field 0.28

Average Number of Countries 0.30

Expected Country Rate Field 0.15

Normalized Citation Rate Field 0.60

Normalized Author Rate Field 0.22

Normalized Country Rate Field 0.25

The average number of citations within journals has a significant positive rank correlation with all 8 other indicators. The highest correlation can be found with the Normalized Citation Rate for the field


Results: Journals, field normalizedKendall’s t Normalized citation rate

Expected Citation Rate Field -0.05**


Expected Authors Rate Field -0.05**


Expected Country Rate Field 0.04**



The average number of citations within journals has a significant positive rank correlation with 4 other indicators. All Expected Rates do not rank correlate. The underlined correlations are even higher than in the previous analysis.


Results: Journals, field normalized

Stepwise regression Step Status Coeff P-value

Average Number of Authors Out -0.016 0.07

Average Number of Countries 3 In 0.35 0.0004

Normalized Author Rate Field 2 In 0.30 0.0000

Normalized Country Rate Field 1 in 1.07 0.0000

In a stepwise regression, the average number of authors is not entered in the model. The relation between the normalized rates holds. Also the average number of countries involved in papers explains additional variance in the regression model. We can conclude that journals that have papers with more authors/countries than we might expect based on their field also have more citations than we expect.


Results: CountriesKendall’s t Average Citations

Expected Citation Rate Journal 0.78


Relative Citation Rate (RCR) 0.56

Mean Normalized Citation Rate (NMCR) 0.71

ECRj/ECRf = NMCR/RCR 0.54


Expected Authors Rate Journal 0.56


Normalized Author Rate Journal 0.21



Expected Country Rate Journal 0.17


Normalized Country Rate Journal 0.12


The average number of citations in countries shows significant rank correlations with all 15 available indicators. Those indicators related to citations show the highest correlations.


Results: CountriesKendall’s t Average Citations RCR NMCR

Expected Citation Rate Journal 0.78 0.35 0.56

Expected Citation Rate Field 0.60 0.28 0.31

Relative Citation Rate (RCR) 0.56 1.00 0.64

Normalized Mean Citation Rate (NMCR) 0.71 0.64 1.00

ECRj/ECRf = NMCR/RCR 0.54 0.30 0.66

Average Number of Authors 0.43 0.30 0.34

Expected Authors Rate Journal 0.56 0.33 0.38

Expected Authors Rate Field 0.51 0.30 0.28

Normalized Author Rate Journal 0.21 0.21 0.21

Normalized Author Rate Field 0.29 0.25 0.30

Average Number of Countries 0.15 0.13 0.17

Expected Country Rate Journal 0.17 0.06 0.22

Expected Country Rate Field 0.07 -0.05 0.09

Normalized Country Rate Journal 0.12 0.14 0.12

Normalized Country Rate Field 0.14 0.15 0.16


Results: Countries – Stepwise RegressionStepwise regression - RCR Step Status Coeff P-value

ECRj/ECRf = NMCR/RCR 1 In 0.5248 0

Average Number of Authors Out 0.7462

Expected Authors Rate Journal Out 0.6761

Expected Authors Rate Field Out 0.2481

Normalized Author Rate Journal Out 0.5329

Normalized Author Rate Field Out 0.7998

Average Number of Countries Out 0.9034

Expected Country Rate Journal Out 0.5138

Expected Country Rate Field 2 In 1.0536 8.60E-03

Normalized Country Rate Journal Out 0.9003

Normalized Country Rate Field Out 0.9324


Results: Countries – Stepwise Regression

Stepwise regression - NMCR Step Status Coeff P-value


In the stepwise regression, the ratio between the two expected citation rates takes a prominent role.

For countries it is safe to conclude that those who score high on normalized citation indicators also tend to publish more in journals that have higher expected citations rates than the field in which they are active.


Results: InstitutesKendall’s t Average Citations

Expected Citation Rate Journal 0.78


Relative Citation Rate (RCR) 0.65

Mean Normalized Citation Rate (NMCR) 0.90

ECRj/ECRf = NMCR/RCR 0.75


Expected Authors Rate Journal 0.47


Normalized Author Rate Journal 0.32



Expected Country Rate Journal 0.40


Normalized Country Rate Journal 0.23


The average number of citations in institutes shows significant rank correlations with all 15 available indicators. Those indicators related to citations show the highest correlations.


Results: InstitutesKendall’s t Average Citations RCR NMCR

Expected Citation Rate Journal 0.78 0.35 0.56

Expected Citation Rate Field 0.40 0.28 0.31

Relative Citation Rate (RCR) 0.65 1.00 0.64

Mean Normalized Citation Rate (NMCR) 0.90 0.64 1.00

ECRj/ECRf = NMCR/RCR 0.75 0.30 0.66

Average Number of Authors 0.40 0.30 0.34

Expected Authors Rate Journal 0.47 0.33 0.38

Expected Authors Rate Field 0.23 0.30 0.28

Normalized Author Rate Journal 0.32 0.21 0.21

Normalized Author Rate Field 0.38 0.25 0.30

Average Number of Countries 0.26 0.13 0.17

Expected Country Rate Journal 0.40 0.06 0.22

Expected Country Rate Field 0.17 -0.05 0.09

Normalized Country Rate Journal 0.23 0.14 0.12

Normalized Country Rate Field 0.26 0.15 0.16


Results: Institutes – Stepwise RegressionStepwise regression / RCR Step Status Coeff P-value




Expected Authors Rate Field 1 In 0.1302 0


Normalized Author Rate Field 5 In -0.0176 0


Expected Country Rate Journal Out 0.0375

Expected Country Rate Field 3 In -0.4312 0

Normalized Country Rate Journal 4 In 0.2217 0



Results: Institutes – Stepwise RegressionStepwise regression / NMCR Step Status Coeff P-value




Expected Authors Rate Field 2 In 0.1326 0


Normalized Author Rate Field 4 In -0.0204 0


Expected Country Rate Journal 5 In -0.3697 0

Expected Country Rate Field Out 0.1624

Normalized Country Rate Journal 3 In 0.2764 0



Conclusions

The introduction of normalized collaboration measures for both multi-authorship and international collaboration helps us in understanding the relation between collaboration and citation scores by enhancing comparability among fields

We observed strong correlations between averages of authors and citations but when we take the normalization into account the correlation does not hold at all levels of aggregation


Conclusions

Countries: Only a correlation between normalized citation scores and journal strategy is observed.

Journals: By applying a field normalization all correlations with field expected collaboration scores dissapear. However, the correlation with normalized collaboration scores remains.

Institutes: Here we see a more scattered image.

collnet expected authorrate

Science

turkey conclusions

international collaboration

turkey data scie

turkey central tendency

single papers

collaboration patterns

different fields

citations glnzel schubert