are people basically good? trust, commerce, and technology at the long tail neel sundaresan
TRANSCRIPT
Are People Basically Good? Trust, Commerce, and Technology at the Long Tail
Neel Sundaresan
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Neel Sundaresan
ISTS, Nov 12, 09
Q1 Q3 Q1 Q3 Q1 Q3 Q1 Q3 Q1 Q3 Q1 Q3 Q1 Q3 Q1 Q3
Listings
546.4Million
1999 2000 2001 2002 20031998 2004 2005
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Neel Sundaresan
ISTS, Nov 12, 09
Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4
Registered Users
180.6Million
1999 2000 2001 2002 20031998 2004 2005
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Neel Sundaresan
ISTS, Nov 12, 09
Then There was One…
$14.83
When asked if he understood that the laser pointer was broken, the buyer said “Of course, I’m a collector of broken laser pointers”
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ISTS, Nov 12, 09
People are Basically Good!
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Neel Sundaresan
ISTS, Nov 12, 09
Divine Reward!
PetroliumJeliffe
$28K
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Neel Sundaresan
ISTS, Nov 12, 09
What a Flake!
CHICAGO - Two sisters from Virginia sold their Illinois-shaped corn flake on eBay Friday night for $1,350."We were biting our nails all the way up to the finish, seeing what would happen," said Melissa McIntire, 23. "There's a lot of relief involved."The winner of the auction, which lasted more than a week, is the owner of a trivia Web site who wants to add the corn flake to a traveling museum.
Illinois-shaped corn flake sells for $1,350Winner of the eBay auction wants to add the flake to a traveling museum
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Neel Sundaresan
ISTS, Nov 12, 09
Heir to Some Hair!
Hair Sold As Washington's Nets $17KSaturday, February 23, 2008
Four strands reportedly clipped from the first president were sold at auction Friday night to a Richmond man who declined to give his name.Colorado resident Christa Allen said her father, a Philadelphia attorney, had given her the hair, which was pressed under glass in a locket and accompanied by a watch.
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Neel Sundaresan
ISTS, Nov 12, 09
Scathing Limbaugh Letter Nets $2.1M
By BRIAN SKOLOFF – Oct 19, 2007
WEST PALM BEACH, Fla. (AP) — A letter from Democratic senators blasting conservative talk show host Rush Limbaugh for using the phrase "phony soldiers" on his program was sold Friday on eBay for a record $2.1 million.
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Neel Sundaresan
ISTS, Nov 12, 09
Up for auction is a composite of all 4 pages of the Harry Reid smear letter and all the signatures into one 8.5 X 31.5 scroll document. The image shown in the auction is cropped for legibility. The acutual document does contain all of the signatures. This will make a great conversation piece and will get the goat of any Rush hating liberal. Would look great in a custom frame or as a Scroll haning on the wall. My cost to print, post & mail is about $10.00. I have a couple more to auction even though I lost money on the 1st one. It is still worth it. PayPal or Money Order. Shipping to US/Canada is $3.00.
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Neel Sundaresan
ISTS, Nov 12, 09
A vehicle sells every 2 minutes
A part or accessory sells every 3 seconds
Diamond jewelry sells every 83 seconds
A Timberland shoe sells every 10 minutes
A trading card sells every 6 seconds
On an average day on eBay…
What wags the Tail?
eBay users trade about $1,400 worth of goods on the site every second.
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Neel Sundaresan
ISTS, Nov 12, 09
The Long Tail Nature
• Buyers outnumber sellers 5:1• Seller-items sold has a power law distribution• Seller-revenue has a power law distribution• Buyer-items bought has a power law distribution
For a sample period over 1 month mean is 3 and median is 1
• Buyer-spent money has a power law distributionFor a sample period of 1 month mean is 98$ and median was 45$
• Categories browsedmean 10.5, median 5
• ~10M new items a day, most items eventually sell, items last from a day to 30 days, most items not cataloged, some auction-some fixed price
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Neel Sundaresan
ISTS, Nov 12, 09
Pareto and the Long Tail
• Vast majority of products appeal to small number of users
• Vast majority of products of this nature can only be carried by small number of sellers
• These account for sizable consumption • “Selling less of more” becomes important
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Neel Sundaresan
ISTS, Nov 12, 09
Britney Spears
Jessica Simpson
Jessica Alba
ChristinaAguileraTara
Reid
LindseyLohan
RainbowBrite
RocketDog
Shoes
Hair
Photo
Poster
dolls
Paris Hilton Perfume
Parikh, Sundaresan
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ISTS, Nov 12, 09
Evolution of Jessica Simpson
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ISTS, Nov 12, 09
The Long Tail is a Fractal!
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Long Tail and Diversity
• Diversity is important to avoid market collapse• The Fractal Nature of the Long Tail helps Diversity • Long Tail affords diversity through “Mass
Customization”
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Neel Sundaresan
ISTS, Nov 12, 09
Lemon Markets and the Long Tail
• Sellers have better knowledge of the goods for sale; buyers don’t
• Buyers have no way of verifying • Seller is incentivised to pass of poor quality goods through
sale as buyer has no way of verifying• Creates market inefficiencies, guarantees are indefinites,
and such markets disappear
George Akerloff, “The Market for Lemons: Quality Uncertainty and Market Mechanism” (1970)
• Bad drives out the Good
Gresham’s Law: “Bad Money (Counterfeits) Drives Good Money out of Circulation”
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Neel Sundaresan
ISTS, Nov 12, 09
Relevance or Merchandizing?
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ISTS, Nov 12, 09
Search Challenge
• Near similar titles“Apple IPOD Nano 4GB Black NEW! Great Deal!”
“Apple IPOD Nano 4GB Black NEW! Skin Great Deal!”
What does someone querying for “ipod nano” look for?
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Search
y = 2121.7x-0.753
R2 = 0.9752
0
500
1000
1500
2000
2500
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
# o
f It
em
s W
on
Rank
Items Won by Searcher vs. Search Result Display Rank
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Neel Sundaresan
ISTS, Nov 12, 09
Reputation
• Sharing of reputation lowers the ability of dishonest agent to profit in the future• Dishonest agents will have to seek new partners – who
will pay only discounted Lemon price : (Trust Discount)• Dishonest agents can still trade outside the coalition
boundaries
• Private Reputation vs Public (Shared) Reputation
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Neel Sundaresan
ISTS, Nov 12, 09
Reputation
• Sharing of reputation lowers the ability of dishonest agent to profit in the future• Dishonest agents will have to seek new partners – who
will pay only discounted Lemon price : (Trust Discount)• Dishonest agents can still trade outside the coalition
boundaries
• Private Reputation vs Public (Shared) Reputation
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Neel Sundaresan
ISTS, Nov 12, 09
Feedback and Networks: Auroral Diagrams
Arts and Crafts Collectibles
Global
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Neel Sundaresan
ISTS, Nov 12, 09
eBay Feedback
• HistoryBefore 1999
Anybody could leave feedback for anybodyNow
Feedbacks are per-transaction between seller and winning bidder• Accumulative
Positive (+1), Negative (-1), Neutral(0)1 line of qualitative textual feedback
• Feedback Profile is publicAny prospective buyer can see all per-transaction feedback with scores
and text• Feedback 2.0
Revealed on multiple aspects of the user feedback• Today
Only buyers can leave feedbacks, sellers can only leave positive feedbacks
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Neel Sundaresan
ISTS, Nov 12, 09
eBay Feedback
• Most Feedbacks are positive (Pollyanna effect)• Negatives are fewer• Fear of retaliation• Satisfaction of receipt• No Feedbacks instead• Positive with text specifying negative experiences• High courtesy Equilibrium (Resnick/Zeckhauser ’01)• Mutually negative feedbacks may represent misplaced blame• Who goes first?
• Since buyer typically pays first, expect seller to go first• Buyer goes first twice as often (Resnick/Zeckhauser ’01)
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Neel Sundaresan
ISTS, Nov 12, 09
Analysis of Feedback Text (Sundaresan et al 2007)
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Neel Sundaresan
ISTS, Nov 12, 09
eBay Feedback – Rated Aspect Summary (Lu, Sundaresan, Zhang – 2009)
• Break down comments into head terms (aspects) and qualifiers (opinions)
• Phase 1: Identify k interesting aspects and cluster data into these – k-means / PLSA / Structured PLSA
• Use priors (Dirichlet) act as training to bias clustering results
• Then use MAP (Max. A Posteriori) to estimate all the parameters
• Phase 2: Identify rating functions for the k aspect clusters using local (per-user) or global rating information
• WWW09 – Lu, Sundaresan, Zhang, “Rated Aspect Summarization” / Thu DM-5 (Opinions) 2:30-4pm
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Neel Sundaresan
ISTS, Nov 12, 09
Expression/Sentiment
• Expression is a metaphor for Trust• When Trust is expressed through feedback or
textual communication it influences mutual Trust and future Trust
• Factors to take into accountWhat a user usually says
What is the change in what the user usually says
How does what someone says affects what the next user says
Only those who have significantly significant things to say do say anything at all
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Neel Sundaresan
ISTS, Nov 12, 09
Do Sellers care about their feedback?
• Sellers can respond to a negative feedbackThe text of the response is displayed below the feedback text
More than a third of the sellers respond to negative feedback
Sound of Silence relates somewhat to fear of retaliatory feedback
• Other studiesBehavioral changes after a negative feedback
Improved behavior vs non-participation
Retaliation
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Neel Sundaresan
ISTS, Nov 12, 09
Trust and Reputation
• Trust is subjective, Reputation is objective• Trust is relative, Reputation is global• Trust is personal, Reputation is collective
A trusts B because B has a good reputation
A trusts B in spite of not knowing B’s reputation
A trusts B in spite of B’s bad reputation
• Reputation may change as Trust between agents change• though Reputation measures cannot be oversensitive to trust
changes
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Neel Sundaresan
ISTS, Nov 12, 09
Transparent vs Opaque Mechanisms
• Transparency helps understand and improve negative behavior
• Opaque is useful to verify mechanism and also evaluate actors and avoid gaming
• Both are important in a reputation system
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Neel Sundaresan
ISTS, Nov 12, 09
Enforcing Trust - Behavioral Economics• Penalizing or Promoting in Ranking• Coupons and Incentives
• (Un)Fortunately,• When enforcements are opaque, strategies to learn the
system• Transparency can be useful but can be gamed
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Neel Sundaresan
ISTS, Nov 12, 09
Motifs: Network-specific properties
• Stamps
• Antiques
-1 0 5 20 100 500 1000 5000 >5000
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Neel Sundaresan
ISTS, Nov 12, 09
Stamps vs Antiques
Trust in Different Categories
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Neel Sundaresan
ISTS, Nov 12, 09
The Continuum of Trust and Fraud
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Neel Sundaresan
ISTS, Nov 12, 09
A Flow Model for Reputation
• Good buyers buy from Trustworthy Sellers• Trustworthy Sellers sell to Good buyers• A mutually recursive equation leads to an equation of the form
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assuming people are basically good!
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Neel Sundaresan
ISTS, Nov 12, 09
Reputation for Augmenting Features
• Reputation ranking makes reputation as integral part of relevance sort
• A Marketplace Search like eBay is complexDiverse items, Diverse sellers, Diverse scenarios
• Reputation has to be combined with relevance and other factors like diversity
• Reputation can used as a ranking function for any feature
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Neel Sundaresan
ISTS, Nov 12, 09
In Summary…
People are basically good
On the MedianAverage
