Santo Fortunato – Reputation and Impact in Academic Careers (Talk at 2nd Annual KNOWeSCAPE Scientific Meeting, http://knowescape.org/knowescape2014-2/)

1. Reputation and impact in
academic careers
Santo Fortunato

2. Acknowledgement s
Francesco Beca7ini Arnab Cha7erjee
Marija Mitrović
Pietro Parolo
Raj K. Pan
Kimmo Kaski
Orion Penner
Alex Petersen
Fabio Pammolli
Massimo Riccaboni
Gene Stanley

3. The role of reputation …
Question: what is the role of author’s reputation on
citation dynamics?
A. M. Petersen, S. F., R. K. Pan, K. Kaski, O. Penner, A. Rungi,
M. Riccaboni, H. E. Stanley, F. Pammolli,
Proc. Natl. Acad. Sci. USA 111, 15316-­‐‑15321 (2014 )

4. Reputation variabl e
Measure of reputation of author i at time t: cumulative
number of citation Ci(t), from the beginning of i’s career until
year t
Issues:
1. H-­‐‑index?
Ci(t) ⇠ hi(t)1+i
2. It does not account for quality: high values of Ci(t) can be
achieved with many low-­‐‑impact papers
3. Effect of reputation of coauthors?
4. It can only grow in time, while reputation may also
decrease (misconduct, fraud)
A. M. Petersen, S. F., R. K. Pan, K. Kaski, O. Penner, A. Rungi,
M. Riccaboni, H. E. Stanley, F. Pammolli,
Proc. Natl. Acad. Sci. USA 111, 15316-­‐‑15321 (2014 )

5. Other variable s
t = Career age, number of years since first publication
⌧ = Paper age, number of years since first citation
Ni(t) = Total number of papers published by i until year t
⌧ c
1/2 = Half-life of paper c
ci,p(t) = Citations of paper p and author i until time t
ci,p(t) = Citations received by paper p of author i in year t
A. M. Petersen, S. F., R. K. Pan, K. Kaski, O. Penner, A. Rungi,
M. Riccaboni, H. E. Stanley, F. Pammolli,
Proc. Natl. Acad. Sci. USA 111, 15316-­‐‑15321 (2014 )

6. Our data
A. Prolific authors of Physical Review Le0ers (PRL) (1958-­‐‑2008)
B. Highly productive physicists
C. Young assistant professors from US Top 50 physics and
astronomy departments
D. Prolific authors of Cell
E. Prolific authors of Annals of Mathematics
Summary
1. 300 physicists
2. 100 biologists
3. 50 mathematicians
A. M. Petersen, S. F., R. K. Pan, K. Kaski, O. Penner, A. Rungi,
M. Riccaboni, H. E. Stanley, F. Pammolli,
Proc. Natl. Acad. Sci. USA 111, 15316-­‐‑15321 (2014 )

7. Reputation and citation
dynamics: cumulativ e
hN0(t)i ⇠ t¯↵, hC0(t)i ⇠ t¯⇣
¯↵ 1, ¯⇣
¯↵
Superlinear algebraic growth!

8. Reputation and citation
dynamics: individual career s
Rank-­‐‑citation profile: discrete generalized β-­‐‑distribution:
c(r) / r!(N + 1 − r)

9. Citation life-­‐‑cycl e
• Citation peak before publication age τ ≈ 5 years
• Slower decay for highly cited papers
• Long half-­‐‑life for papers in math

10. Citation life-­‐‑cycle: half-­‐‑life
versus number of citation s
¯⌦
⌧1/2 ⇠ c¯⌦p
ranges from 0.3 for Biology to 1 for Mathematics
(uniformly distributed impact across time)

11. The reputation mode l
ci,p(t + 1) vs cp(t) ?
Preferential a7achment?
For cp(t) lower than a threshold cx the number of cites
exceeds that predicted by preferential a7achment: why?

12. The reputation mode l
!ci,p(t + 1) ⌘⌘ ⇥ ⇧p(t) ⇥ A⇢(⌧ ) ⇥ Ri(t) =
=⌘ [cp(t)]⇡ exp(−⌧p/¯⌧) [Ci(t)]⇢
noise
preferential
a7achment
life cycle
reputation
Regression model
Main result:
⇢(c cx) ⇢(c cx), ⇡(c cx) ⇡(c cx)
⇢(c ! cx) ⇡ 0

13. The reputation mode l
Citations are initially boosted by author reputation up to a
tipping point cx above which the citation rate is sustained
mostly by publication reputation
Example (aggregated dataset A/B)
⇢(c cx = 40) ⇡ 0.2, ⇢(c cx = 40) ⇡ 0
⇡(c cx = 40) ⇡ 0.4, ⇡(c cx = 40) ⇡ 1
For two scientists such that C1(t)=10 C2(t):
c1(t)/c2(t) = 10⇢ ⇡ 1.66 (c cx = 40)
66 % increase for each 10-­‐‑fold increase in Ci(t) !

15. The Nobel Prize Delay
60
50
40
30
20
10
0
Physics
Data
Average
Model
1900
1925
1950
1975
2000
Time between discovery prize
Chemistry
Physiology or Medicine
1900
1925
1950
1975
2000
1900
1925
1950
1975
2000
Year of nobel award
F. Beca7ini, A. Cha7erjee, S. F, M. Mitrović, R. K. Pan, P.
Della Brio7a Parolo, Natur e 508, 186 (2014)
h7p://scitation.aip.org/content/aip/magazine/physicstoday/
news/10.1063/PT.5.2012

16. The Nobel Prize Delay
F. Beca7ini, A. Cha7erjee, S. F, M. Mitrović, R. K. Pan, P.
Della Brio7a Parolo, Natur e 508, 186 (2014)
h7p://scitation.aip.org/content/aip/magazine/physicstoday/
news/10.1063/PT.5.2012

17. The Nobel Prize Delay
F. Beca7ini, A. Cha7erjee, S. F, M. Mitrović, R. K. Pan, P.
Della Brio7a Parolo, Natur e 508, 186 (2014)
h7p://scitation.aip.org/content/aip/magazine/physicstoday/
news/10.1063/PT.5.2012

20. Outlook
• Author reputation drives the initial phase of the
citation dynamics of papers
• After a tipping point, citation accumulation is driven by
the paper’s own reputation
• Tip: look for quality!
• The lag between discovery and the Nobel prize is
growing rapidly
• Extinction of worthy winners?
• Decay of (fundamental) science?

21. Organizing commi7ee: S. Fortunato (Aalto), A. Gionis (Aalto), H. Hämmäinen (Aalto),
K. Kaski (Aalto), W. Quahrociocchi (IMT), J. Saramäki (Aalto), J. Valimäki (Aalto)

22. Lada Adamic
Facebook
Sinan Aral
MIT
László Barabási
Northeastern U.
Nicholas Christakis
Yale
Robin Dunbar
Oxford
Andreas Flache
Gröningen
Dirk Helbing
ETH Zürich
Ma7hew Jackson
Stanford
Jure Leskovec
Stanford
Alex Pentland
MIT
David Lazer
Northeastern U.
Alex Vespignani
Northeastern U.
Duncan Wa7s
Microsoft
Michael Macy
Cornell

23. www.iccss2015.eu
#ICCSS2015 @ICCSS2015