Information Contagion: An Empirical Study of the Spread of News
on Digg and Twitter Social Networks
Kris%naLermanRumiGhosh
USCInforma,onSciencesIns,tute
USC Information Sciences Institute
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OnlineSocialNetworks
Onlinesocialnetworkshavebecomeimportantchannelsforthespreadof,melyandrelevantinforma,on
poweredbyTouchGraph
USC Information Sciences Institute
Informa%onflowonnetworks
hGp://www.flickr.com/photos/27318782@N03/4639307923
3
Network2Network1
http://www.flickr.com/photos/27318782@N03/4639307471/
USC Information Sciences Institute
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DynamicsofSocialInforma%on
USC Information Sciences Institute
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Socialnews:Digg
Userssubmitandvotefor(digg)newsstories
Usersjoinnetworkstosee• Storiesfriendssubmit
• Storiesfriendsvotefor
Diggfeaturesstorieswithmostvotesonitsfrontpage
USC Information Sciences Institute
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Socialnews:TwiDer+TweetmemeUserstweetandretweet*URLstonewsstories
*‘Retweet’=tweetsomeoneelse’spost
“RT@xfailedbombplothGp://bit.ly/xmas09”
Usersjoinnetworkstosee• Tweetsbyuserstheyfollow• Retweetsbyuserstheyfollow
TweetmemeaggregatesalltweetsandfeaturesmostretweetedURLsonitsfrontpage
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Socialnews:Datasets
Digg• Stories
• 3,553stories,promotedinJune,2009
• TimesubmiGed,promoted• Votesforeachstory
• Timeofthevote• Nameofvoter
• Ac,veusers• 139,409whovotedforatleast
onestory• 71,834ofthemfollowingat
leastoneuser• 258,220links• fannetwork
TwiGer• Stories
• 398mostretweetedstories6/11/09—7/3/09
• extractedfromTweetmeme• Retweetsofeachstory
• <1000mostrecentretweets• Timeofretweet&username
• Ac,veusers• 137,582whoretweetedatleast
onestory• Following/followerrela,ons
throughTwiGerAPI• 6,200,051links• followernetwork
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Ques%ons
USC Information Sciences Institute
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Basicterms
SubmiGer• userwhosubmiGedlinktoastory• userwhofirsttweetedlinktoastory
Vote• digg• retweet
FanofuserA• userwatchingA’sac,vityonDigg• userfollowingAonTwiGer
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Userac%vity:distribu%onoffans
TwiGerDigg
• TypicalnumberoffollowersonTwiGer~10,butcanbemillions• NotypicalnumberoffansonDigg–“longtail”
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Userac%vity:distribu%onofvo%ng
TwiGer
• “Longtail”distribu,onofuserac,vity• Differenceinsloperelatedtoeffortofac,vity[cfWilkinson2008]
Digg
USC Information Sciences Institute
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Dynamicsofstories
Digg TwiGer
1:U.S.GovernmentAsksTwiGertoStayUpfor#IranElec,on2:WesternCorpora,onsHelpedCensorIranianInternet3:Iranianclericsdefyayatollah,joinprotests
1:USgovaskstwiGertostayup2:IranHasBuiltaCensorshipMonsterwithhelpofwesttech3:ClericsjoinIran’san,‐governmentprotests‐CNN.com
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Dynamicsofstories
Digg TwiGer
• Twodis,nctphasesforDiggstories:upcomingandpromoted• Numberofvotesonbothsitessaturatesaveroneday• Saturatedvaluereflectsstorypopularity
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Popularityofstories
Digg TwiGer
lognormalfit lognormalfit
• AggregateoverallstoriestofactoroutinfluenceofsubmiGerandstoryquality• “Inequalityofpopularity”–somestoriesmuchmorepopularthanothers
cfsocialinfluencestudyof[Salganik,Dodds&WaGs,2006]
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Informa%onflowonnetworks
Informa,onspreadsonanetworkasfans(followers)votefor(retweet)storiestheirfriendssubmitorvotefor.
…fanvotes–i.e.,votesfromfans
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Dynamicsofinforma%onspreadonnetworks
Digg TwiGer
fan
vote
s
follo
wer
retw
eets
• Evolu,onoffanvotesqualita,velysimilartothatofallvotes
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Howfardoesinforma%onspreadonnetworks?
Digg TwiGer
normalfitnormalfit
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Howfardoesinforma%onspreadamongsubmiDer’sfans?
numberofretweetsfromsubmiDer’sfollowers
Digg TwiGer
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Howfastdoesinforma%onspreadonnetworks?
• Twodis,nctphasesonDigg:storiesspreadfasterthroughthenetworkbeforepromo,onthanaverwards• TwiGerstoriesspreadatauniformrate,butwithgreatervariability
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Howfastdoesinforma%onspreadonnetworks?
Probabilitynextvoteisfromafan
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Networkstructure
Networksamplesize• Digg:279,725users• TwiGer:6,200,051users
Networkdensity• Frac,onofreciprocallinks(i.e.,mutualfans)
• Digg:fm=3.20x10‐6• TwiGer:fm=2.07x10‐7
• Modifiedclusteringcoefficient(frac,onofcycles,e.g.,ABCA)
• Digg:fc=7.60x10‐12• TwiGer:fc=1.92x10‐14
Diggnetworkisdenser,moreinter‐connectedthanTwiGer’s
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Summaryofresults
Networkstructureandinforma,onflow• Digg’snetworkisdenserthanTwiGer’s
• Newsspreadsfasterini,allythroughDigg’snetworkthanTwiGer’s• But,itdoesnotspreadasfarasonTwiGer• FanswhovoteforastoryonDiggarealsosubmiGer’sfans
• TwiGer’snetworkissparse• FansunconnectedtosubmiGerhelpspreadthestory
Userinterfaceandinforma,onflow• Beforepromo,on,Diggstoriesspreadmainlythroughthenetwork
• SimilartostoryspreadonTwiGer
• Averpromo,on,storiesspreadmainlyoutsidethenetwork• Promo,onincreasesstoryvisibilityoutsidethenetwork
• NoequivalentmechanismonTwiGer
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Relatedwork
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Conclusion
Compara,veempiricalanalysisofonlinesocialnetworksandsocialnewsonDiggandTwiGer
• Similari,es• Networksareusedonbothsitestospreadnews• Informa,onflowonDiggbeforepromo,onissimilartoinforma,onflow
onTwiGer
• Differencesindynamicscanbeexplainedbyuserinterfaceandnetworkdensity• Digg’suserinterfacegiveshighvisibilitytopromotedstories
• Promo,onslowsinforma,onspread
• Digg’snetworkisdenserthanTwiGer’s• Affectshowfastandhowfarnewsspreads
• Dynamicsofinforma,onflowasagaugeofinforma,onquality• SocialdynamicsofDigg[Hogg&Lerman,poster][Lerman&Hogg,WWW2010]
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