Bowling Alone and Trust Decline in Social Network Sites

Bowling Alone and Trust Decline in Social Network Sites
Paolo Massa , Martino Salvetti, Danilo Tomasoni
FBK - Trento, Italy
[email_address]
http://www.gnuband.org
License: Creative Commons (see last slide for details)‏

Outline
1. Social Network Sites and Trust Networks
2. Longitudinal SNA on Advogato.org (over 4 years) and related work
3. Experiments and Results

Social Network Site (SNS)‏
“ Web-based services that allow individuals to
(1) construct a public or semi-public profile within a bounded system,
(2) articulate a list of other users with whom they share a connection, and
(3) to view and traverse their list of connections and those made by others within the system.
The nature and nomenclature of these connections may vary from site to site.” [boyd]

Social Network Sites
Social networks: Facebook, Flickr, Youtube, del.icio.us
BUT ALSO
E-marketplaces: Ebay.com, Epinions.com, Amazon.com
News sites: Slashdot.org, Kuro5hin.org, Digg.com
Job sites: LinkedIn, Ryze, ...
Open Source Developer communities: Advogato , Github
Hosting networks: Couchsurfing, Hospitalityclub
Great opportunity for research!

Trust statements expressed by raph

Advogato trust network
Advogato = SNS for Open Source developers
http://www.advogato.org
Possible to express trust in other users on 4 levels:
Master (mapped as T(A,B)= 1.0 in [0,1])
Journeyer (mapped as T(A,B)= 0.8 in [0,1])‏
Apprentice (mapped as T(A,B)= 0.6 in [0,1])‏
Observer (mapped as T(A,B)= 0.4 in [0,1])‏
WEIGHTED RELATIONSHIPS!!!

What is trust?
Definition
[PICTURE]

What is trust?
Definition
[PICTURE]
Trust statement is an explicit judgement
given by a user about another user:
Example:
” I (Alice) trusts Bob as 0.6 in [0,1]”
Very general definition: it fits many situations (Flickr, Facebook, Linkedin, Ebay, ...)‏
Alice Bob 0.6

What is trust?
Definition
[PICTURE]
Aggregate all the trust statements to produce a trust network
Node ~ user
Direct edge ~ trust statement
Properties of Trust:
- weighted (0=distrust, 1=max trust)‏
- subjective
- asymmetric
- context dependent
0.9 1 0.2 Alice Carol Bob 0 Dave 0.6

What is trust?
Definition
[PICTURE]
CLAIM
Possible to adopt the trust network metaphor for every social network site (facebook, flickr, delicious, ... the web too)‏
Why Advogato? Today is the only one with Weighed directed trust relationships available

Outline

Advogato social network datasets
Collected many snapshots of the social network (60+)
First dataset: 2000 -02-25 (early days, 300 users)
Last dataset: 2004 -10-28 (mature community)‏
(all datasets released on www.Trustlet.org)‏
We studied evolution of trust in time in a community

Related work
1) Social networks topology (and evolution): here we study trust relationships
2) WorldValuesSurvey 1000+ interviewees for 97 countries (1981 to 2007)
One question: “Would you say that most people can be trusted?” mid-1990s: “yes” ranges from 65% (Norway) to 3% (Brazil)‏
Trust correlates positively with economy growth and welfare. Negatively with inequality and corruption. Studies on evolution of trust over time.
3) Putnam “Bowling alone: America's Declining Social Capital” [putnam]: ~500,000 interviews in US (1975-2000) -> decline of social capital over time (belong to fewer orgs (-58%), know their neighbors less (-35%), ...)‏
Motivation for this work : Is it possible to study evolution of trust as the last 2 examples BUT at the finer-grained level of the single human?
Yes! Thanks to Social Network Sites! Here we analyze a real social network (“I trust Mary as 0.6”) and not answer to interviews! Just a beginning!

Outline

Experiments on Advogato networks
- basic statistics such as number of nodes and edges
- traditional social network analysis indexes such as clustering and mean degree of separation
- measures related to weighted trust such as frequency of trust statements, discordance in reciprocated trust statements and changes in average trust
(all of them over 4 years time!)‏

What I'm going to show you? A measure (y axis)‏ over time (x axis)‏ So its evolution in time Up to 2004 -10-28 Since 2000 -02-25 All datasets and Python code released on www.trustlet.org (Test your hypos!)‏

Number of users on Advogato 300 users (in 2000-02-25)‏ 6482 users (in 2004-10-28)‏ Evolution from a close-knit circle (first users knew the funders and each other)‏ to a mature society (new users joined it via web)‏

Number of trust edges on Advogato 2109 trust edges (in 2000-02-25)‏ 47943 trust edges (in 2004-10-28)‏ As expected, #edges, just as #users, grows

Mean outdegree (outgoing trust statements per user)‏ Surprised? It's a REAL social network! Important to study REAL social network and not synthetized ones because of un- expected activity patterns (1) 2000-02-25: 14.0 (300 users)‏ (2) 2000-07-18: 16.7 (1454 users)‏ what did the 1154 new users did in 5 months? No datasets ;( (3) 2000-08-11: 15.1 (1880 users)‏

% users in the main strongly connected component (set in which everyone is reachable by everyone)‏ Decline from 62% down to 48% In the ol' days, everyone knew each other, then, new unknown users start to join (smaller subcommunities)‏ ...

Clustering coefficient Same pattern: decline! The network becomes more spread over time

Mean degrees of separation (stabilizes over 3.5)‏ Not SIX??? 6 degrees of separation is more a buzzword than reality

Percentage of trust statements that get reciprocated In Advogato, it stabilizes ~36% In Flickr, ~66% Facebook, 100% by design (depends on the socio-technological system)‏

Reciprocation matrix: what (row) reciprocated how (column)‏

What is trust?
Definition
[PICTURE]

% trust values on edges

Average trust in the community as expressed by Advogato users over time Trust is declining as society grows. A normal pattern common to every society?

Conclusions
First longitudinal analysis of trust evolution in a social community (4 years, from 300 users to ~6500)‏
Experimental evidence of trust decline
Goal: create real-time global trust monitor (social relationships in time from all social network sites!)‏
For now, datasets and python code released at www.trustlet.org

Bibliography
[boyd] boyd, d. and Ellison, N. (2007). Social network sites: Definition, history, and scholarship. Journal of Computer-Mediated Communication, 13(1):210-230.
[newman] Newman, M. E. J. (2001). Clustering and preferential attachment in growing networks. Phys. Rev. E 64
[mislove] Mislove, A., Koppula, H. S., Gummadi, K. P., Druschel, P., and Bhattacharjee, B. (2008). Growth of the flickr social network. In WOSP '08: Proceedings of the first workshop on Online social networks, pages 25-30, New York, NY, USA. ACM.
[putnam] Putnam, R. D. (1995). Bowling Alone: America's Declining Social Capital. Journal of Democracy, Volume 6, Number 1
[barabasi] Barabasi, A.-L. (2003). Linked: How Everything is Connected to Everything Else and What it Means for Business and Everyday Life. Plume Books.

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Bowling Alone and Trust Decline in Social Network Sites

by Paolo Massa on Jan 28, 2010

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