Reputation and Impact in Academic Careers

Reputation and impact in academic careers Santo Fortunato

Acknowledgements

Pietro Parolo

Marija Mitrović Arnab Cha7erjee Francesco Beca7ini

Raj K. Pan

Kimmo Kaski

Orion Penner Alex Petersen

Fabio Pammolli

Massimo Riccaboni Gene Stanley

The role of reputation …

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)

Question: what is the role of author’s reputation on citation dynamics?

Reputation variable



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? 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)

Ci(t) ⇠ hi(t)1+�i

Other variables



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

⌧ c1/2 = 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

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

1.  300 physicists 2.  100 biologists 3.  50 mathematicians

Summary



Reputation and citation dynamics: cumulative

hN 0(t)i ⇠ t↵̄, hC 0(t)i ⇠ t⇣̄

↵̄ & 1, ⇣̄ > ↵̄

Superlinear algebraic growth!

Reputation and citation dynamics: individual careers

c(r) / r��(N + 1� r)�Rank-‐‑citation profile: discrete generalized β-‐‑distribution:

Citation life-‐‑cycle

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

Citation life-‐‑cycle: half-‐‑life versus number of citations

⌦̄

⌧1/2 ⇠ c⌦̄p

ranges from 0.3 for Biology to 1 for Mathematics (uniformly distributed impact across time)

The reputation model �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?

The reputation model

�ci,p(t+ 1) ⌘ ⌘ ⇥⇧p(t)⇥A⇢(⌧)⇥Ri(t) =

= ⌘ [cp(t)]⇡exp(�⌧p/⌧̄) [Ci(t)]

⇢

noise preferential a7achment

life cycle reputation

Regression model

⇢(c < cx

) > ⇢(c � cx

), ⇡(c < cx

) < ⇡(c � cx

)Main result:

⇢(c � cx

) ⇡ 0

The reputation model

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) !

Citations are initially boosted by author reputation up to a tipping point cx above which the citation rate is sustained mostly by publication reputation

The Nobel Prize Delay

F. Beca7ini, A. Cha7erjee, S. F, M. Mitrović, R. K. Pan, P. De l l a B r i o7a Pa ro lo , Na tu r e 5 08 , 1 86 ( 2 014 ) h7p://scitation.aip.org/content/aip/magazine/physicstoday/news/10.1063/PT.5.2012

1900

1925

1950

1975

2000

0

10

20

30

40

50

60

Tim

ebet

wee

ndis

cover

y&

pri

zePhysics

DataAverageModel

1900

1925

1950

1975

2000

Chemistry

Year of nobel award19

0019

2519

5019

7520

00

Physiology or Medicine

The Nobel Prize Delay

F. Beca7ini, A. Cha7erjee, S. F, M. Mitrović, R. K. Pan, P. De l l a B r i o7a Pa ro lo , Na tu r e 5 08 , 1 86 ( 2 014 ) h7p://scitation.aip.org/content/aip/magazine/physicstoday/news/10.1063/PT.5.2012

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?

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

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

Alex Vespignani Northeastern U.

Duncan Wa7s Microsoft

David Lazer Northeastern U.

Michael Macy Cornell

www.iccss2015.eu #ICCSS2015 @ICCSS2015

Reputation and Impact in Academic Careers

Science

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