Prof. Panos Ipeirotis Search and the New Economy Session 5 Mining User-Generated Content

Prof. Panos Ipeirotis

Search and the New Economy

Session 5

Mining User-Generated Content

Today’s Objectives

• Tracking preferences using social networks– Facebook API– Trend tracking using Facebook

• Mining positive and negative opinions– Sentiment classification for product reviews– Feature-specific opinion tracking

• Economic-aware opinion mining– Reputation systems in marketplaces– Quantifying sentiment using econometrics

Top-10, Zeitgeist, Pulse, …

• Tracking top preferences have been around for ever

Online Social Networking Sites

• Preferences listed and easily accessible

Facebook API

• Content easily extractable

• Easy to “slice and dice”– List the top-5 books for 30-year old New Yorkers– List the book that had the highest increase across

female population last week– …

Demo





Customer-generated Reviews

• Amazon.com started with books

• Today there are review sites for almost everything

• In contrast to “favorites” we can get information for less popular products

Questions

• Are reviews representative?

• How do people express sentiment?

Rating(1 … 5 stars)

Helpfulness of review(by other customers)

Review

Do People Trust Reviews?

• Law of large numbers: single review no, multiple ones, yes

• Peer feedback: number of useful votes

• Perceived usefulness is affected by:– Identity disclosure: Users trust real people– Mixture of objective and subjective elements– Readability, grammaticality

• Negative reviews that are useful may increase sales! (Why?)

Are Reviews Representative?

1 2 3 4 5

cou

nts

1 2 3 4 5

cou

nts　

1 2 3 4 5

cou

nts

1 2 3 4 5

cou

nts

Guess?

What is the Shape of the Distribution of Number of Stars?

Observation 1: Reporting Bias　

1 2 3 4 5

cou

nts

Why?

Implications for WOM strategy?

Possible Reasons for Biases

• People don’t like to be critical

• People do not post if they do not feel strongly about the product (positively or negatively)

Observation 2: The SpongeBob Effect

SpongeBob Squarepants Oscar

versus

Oscar Winners 2000-2005

Average Rating 3.7 Stars

SpongeBob DVDs

Average Rating 4.1 Stars

And the Winner is… SpongeBob!

If SpongeBob effect is common, then ratings do not accurately signal the quality of the resource

What is Happening Here?

• People choose movies they think they will like, and often they are right– Ratings only tell us that “fans of SpongeBob like SpongeBob”– Self-selection

• Oscar winners draw a wider audience– Rating is much more representative of the general population

• When SpongeBob gets a wider audience, his ratings drop

Title # Ratings Ave

SpongeBob Season 2 3047 4.12

Tide and Seek 3114 4.05

SpongeBob the Movie 21,918 3.49

Home Sweet Pineapple 2007 4.10

Fear of a Krabby Patty 1641 4.06

Effect of Self-Selection: Example

• 10 people see SpongeBob’s 4-star ratings– 3 are already SpongeBob fans, rent movie, award 5 stars– 6 already know they don’t like SpongeBob, do not see

movie– Last person doesn’t know SpongeBob, impressed by high

ratings, rents movie, rates it 1-star

Result:• Average rating remains unchanged: (5+5+5+1)/4

= 4 stars• 9 of 10 consumers did not really need rating

system• Only consumer who actually used the rating

system was misled

Bias-Resistant Reputation System

• Want P(S) but we collect data on P(S|R)S = Are satisfied with resourceR = Resource selected (and reviewed)

• However, P(S|E) P(S|E,R) E = Expects that will like the resource

– Likelihood of satisfaction depends primarily on expectation of satisfaction, not on the selection decision

– If we can collect prior expectation, the gap between evaluation group and feedback group disappears

• whether you select the resource or not doesn’t matter

Bias-Resistant Reputation System

Before viewing:• I think I will:

Love this movie Like this movie It will be just OK Somewhat dislike this movie Hate this movie

After viewing:• I liked this movie:

Much more than expected More than expected About the same as I expected Less than I expected Much less than I expected

Big fans

Everyone else

Skeptics

Conclusions

1. Reporting bias and Self-selection bias exists in most cases of consumer choice

2. Bias means that user ratings do not reflect the distribution of satisfaction in the evaluation group– Consumers have no idea what “discount” to apply to

ratings to get a true idea of quality

3. Many current rating systems may be self-defeating– Accurate ratings promote self-selection, which leads to

inaccurate ratings

4. Collecting prior expectations may help address this problem

OK, we know the biases

• Can we get more knowledge?

• Can we dig deeper than the numeric ratings?– “Read the reviews!”– “They are too many!”

Independent Sentiment Analysis

• Often we need to analyze opinions– Can we provide review summaries? – What should the summary be?

Basic Sentiment classification

• Classify full documents (e.g., reviews, blog postings) based on the overall sentiment– Positive, negative and (possibly) neutral

• Similar but also different from topic-based text classification.– In topic-based classification, topic words are important

• Diabetes, cholesterol health• Election, votes politics

– In sentiment classification, sentiment words are more important, e.g., great, excellent, horrible, bad, worst, etc.

– Sentiment words are usually adjectives or adverbs or some specific expressions (“it rocks”, “it sucks” etc.)

• Useful when doing aggregate analysis

Can we go further?

• Sentiment classification is useful, but it does not find what the reviewer liked and disliked.

– Negative sentiment does not mean that the reviewer does not like anything about the object.

– Positive sentiment does not mean that the reviewer likes everything

• Go to the sentence level and feature level

Extraction of features

• Two types of features: explicit and implicit

• Explicit features are mentioned and evaluated directly– “The pictures are very clear.”– Explicit feature: picture

• Implicit features are evaluated but not mentioned– “It is small enough to fit easily in a coat pocket or purse.”– Implicit feature: size

• Extraction: Frequency based approach– Focusing on frequent features (main features)– Infrequent features can be listed as well

Identify opinion orientation of features

• Using sentiment words and phrases– Identify words that are often used to express positive or

negative sentiments – There are many ways (dictionaries, WorldNet, collocation with

known adjectives,…)

• Use orientation of opinion words as the sentence orientation, e.g., – Sum:

• a negative word is near the feature, -1, • a positive word is near a feature, +1

Two types of evaluations

• Direct Opinions: sentiment expressions on some objects/entities, e.g., products, events, topics, individuals, organizations, etc– E.g., “the picture quality of this camera is great”– Subjective

• Comparisons: relations expressing similarities, differences, or ordering of more than one objects.– E.g., “car x is cheaper than car y.”– Objective or subjective– Compares feature quality– Compares feature existence

Visual Summarization & Comparison

Summary

Picture Battery Size Weight Zoom

+

_

Comparison

_

+

Digital camera 1

Digital camera 1

Digital camera 2

Example: iPod vs. Zune





Comparative Shopping in e-Marketplaces

Customers Rarely Buy Cheapest Item

Are Customers Irrational?

$11.04

BuyDig.com gets

Price Premium(customers pay more than

the minimum price)

Price Premiums @ Amazon

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-100 -75 -50 -25 0 25 50 75 100

Price Premium

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Irrational (?

)

Why not Buying the Cheapest?

You buy more than a product

Customers do not pay only for the product

Customers also pay for a set of fulfillment characteristics

Delivery

Packaging

Responsiveness

…

Customers care about reputation of sellers!

Reputation Systems are Review Systems for Humans

Example of a reputation profile

Basic idea

Conjecture: Price premiums measure reputation

Reputation is captured in text feedback

Examine how text affects price premiums(and do sentiment analysis as a side effect)

Outline

• How we capture price premiums

• How we structure text feedback

• How we connect price premiums and text

Data

Overview

Panel of 280 software products sold by Amazon.com X 180 days

Data from “used goods” market

Amazon Web services facilitate capturing transactions

No need for any proprietary Amazon data

Data: Secondary Marketplace

Data: Capturing Transactions

time

Jan 1 Jan 2 Jan 3 Jan 4 Jan 5 Jan 6 Jan 7 Jan 8

We repeatedly “crawl” the marketplace using Amazon Web Services

While listing appears item is still available no sale

Data: Capturing Transactions

time

Jan 1 Jan 2 Jan 3 Jan 4 Jan 5 Jan 6 Jan 7 Jan 8 Jan 9 Jan 10

We repeatedly “crawl” the marketplace using Amazon Web Services

When listing disappears item sold

Capturing transactions and “price premiums”

Data: Transactions

When item is sold, listing disappears

time

Item sold on 1/9

Jan 1 Jan 2 Jan 3 Jan 4 Jan 5 Jan 6 Jan 7 Jan 8 Jan 9 Jan 10

Data: Variables of Interest

Price Premium

Difference of price charged by a seller minus listed price of a competitor

Price Premium = (Seller Price – Competitor Price)

Calculated for each seller-competitor pair, for each transaction

Each transaction generates M observations, (M: number of competing sellers)

Alternative Definitions:

Average Price Premium (one per transaction)

Relative Price Premium (relative to seller price)

Average Relative Price Premium (combination of the above)

Price premiums @ Amazon

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-100 -75 -50 -25 0 25 50 75 100

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Average price premiums @ Amazon

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-100 -75 -50 -25 0 25 50 75 100

Average Price Premium

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Relative Price Premiums

-1--0.9

-0.9--0.8

-0.8--0.7

-0.7--0.6

-0.6--0.5

-0.5--0.4

-0.4--0.3

-0.3--0.2

-0.2--0.1

-0.1-0.0

0-0.1 0.1-0.2

0.2-0.3

0.3-0.4

0.4-0.5

0.5-0.6

0.6-0.7

0.7-0.8

0.8-0.9

0.9-10

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Average Relative Price Premiums

-1--0.9

-0.9--0.8

-0.8--0.7

-0.7--0.6

-0.6--0.5

-0.5--0.4

-0.4--0.3

-0.3--0.2

-0.2--0.1

-0.1-0.0

0-0.1 0.1-0.2

0.2-0.3

0.3-0.4

0.4-0.5

0.5-0.6

0.6-0.7

0.7-0.8

0.8-0.9

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Outline




Decomposing Reputation

Is reputation just a scalar metric?

Many studies assumed a “monolithic” reputation

Instead, break down reputation in individual components

Sellers characterized by a set of fulfillment characteristics(packaging, delivery, and so on)

What are these characteristics (valued by consumers?)

We think of each characteristic as a dimension, represented by a noun, noun phrase, verb or verbal phrase (“shipping”, “packaging”, “delivery”, “arrived”)

Use (simple) Natural Language Processing tools

Scan the textual feedback to discover these dimensions

Decomposing and Scoring Reputation

Decomposing and scoring reputation

We think of each characteristic as a dimension, represented by a noun or verb phrase (“shipping”, “packaging”, “delivery”, “arrived”)

The sellers are rated on these dimensions by buyers using modifiers (adjectives or adverbs), not numerical scores

“Fast shipping!”

“Great packaging”

“Awesome unresponsiveness”

“Unbelievable delays”

“Unbelievable price”

How can we find out the meaning of these adjectives?

Structuring Feedback Text: Example

Parsing the feedback

P1: I was impressed by the speedy delivery! Great Service!

P2: The item arrived in awful packaging, but the delivery was speedy

Deriving reputation score

We assume that a modifier assigns a “score” to a dimension α(μ, k): score associated when modifier μ evaluates the k-th dimension

w(k): weight of the k-th dimension

Thus, the overall (text) reputation score Π(i) is a sum:

Π(i) = 2*α (speedy, delivery) * weight(delivery)+ 1*α (great, service) * weight(service) +

1*α (awful, packaging) * weight(packaging)

unknownunknown?

Outline




Sentiment Scoring with Regressions

Scoring the dimensions

Use price premiums as “true” reputation score Π(i) Use regression to assess scores (coefficients)

Regressions

Control for all variables that affect price premiums

Control for all numeric scores of reputation

Examine effect of text: E.g., seller with “fast delivery” has premium $10 over seller with “slow delivery”, everything else being equal

“fast delivery” is $10 better than “slow delivery”

estimated coefficients

Π(i) = 2*α (speedy, delivery) * weight(delivery)+ 1*α (great, service) * weight(service) +

1*α (awful, packaging) * weight(packaging)

PricePremium

Some Indicative Dollar Values

Positive Negative

Natural method for extracting sentiment strength and polarity

good packaging -$0.56

Naturally captures the pragmatic meaning within the given context

captures misspellings as well

Positive? Negative?

Results

Some dimensions that matter

Delivery and contract fulfillment (extent and speed)

Product quality and appropriate description

Packaging

Customer service

Price (!)

Responsiveness/Communication (speed and quality)

Overall feeling (transaction)

More Results

Further evidence: Who will make the sale?

Classifier that predicts sale given set of sellers

Binary decision between seller and competitor

Used Decision Trees (for interpretability)

Training on data from Oct-Jan, Test on data from Feb-Mar

Only prices and product characteristics: 55%

+ numerical reputation (stars), lifetime: 74%

+ encoded textual information: 89%

text only: 87%

Text carries more information than the numeric metrics

Other applications

Summarize and query reputation data

Give me all merchants that deliver fast

SELECT merchant FROM reputation

WHERE delivery > ‘fast’

Summarize reputation of seller XYZ Inc.

Delivery: 3.8/5

Responsiveness: 4.8/5

Packaging: 4.9/5

Pricing reputation

Given the competition, merchant XYZ can charge $20 more and still make the sale (confidence: 83%)

Seller: uCameraSite.com

1. Canon Powershot x300

2. Kodak - EasyShare 5.0MP

3. Nikon - Coolpix 5.1MP

4. Fuji FinePix 5.1

5. Canon PowerShot x900

Your last 5 transactions in Cameras

Name of product Price

Seller 1 - $431

Seller 2 - $409

You - $399

Seller 3 - $382

Seller 4-$379

Seller 5-$376

Canon Powershot x300

Your competitive landscapeProduct Price (reputation)

(4.8)

(4.65)

(4.7)

(3.9)

(3.6)

(3.4)

Your Price: $399Your Reputation Price: $419Your Reputation Premium: $20 (5%)

$20

Left on the table

Reputation Pricing Tool for Sellers

25%

14%

7%

45%

9%

Quantitatively Understand & Manage Seller Reputation

How your customers see you relative to other sellers:

35%*

69%

89%

82%

95%

Service

Packaging

Delivery

Overall

Quality

Dimensions of your reputation and the relative importance to your customers:

Service

Packaging

Delivery

Quality

Other* Percentile of all merchants

• RSI Products Automatically Identify the Dimensions of Reputation from Textual Feedback• Dimensions are Quantified Relative to Other Sellers and Relative to Buyer Importance• Sellers can Understand their Key Dimensions of Reputation and Manage them over Time• Arms Sellers with Vital Info to Compete on Reputation Dimensions other than Low Price.

Tool for Seller Reputation Management

Marketplace Search

Used Market (ex: Amazon)

Price Range $250-$300

Seller 1 Seller 2

Seller 4 Seller 3

Sort by Price/Service/Delivery/other dimensions

Canon PS SD700

Service

Packaging

Delivery

Price

Dimension Comparison

Seller 1

Price Service Package Delivery

Seller 2

Seller 3

Seller 4

Seller 5

Seller 6

Seller 7

Tool for Buyers

Summary

• User feedback defines reputation → price premiums

• Generalize: User-generated-content affects “markets”• Reviews and product sales• News/blogs and elections

• Examine changes in demand and estimate weights of features and strength of evaluations

Product Reviews and Product Sales

“poor lenses”

+3%

“excellent lenses”

-1%

“poor photos”

+6%

“excellent photos”

-2%

Feature “photos” is two time more important than “lenses” “Excellent” is positive, “poor” is negative “Excellent” is three times stronger than “poor”

Question: Reviews and Ads

• How?

• Is your strategy incentive-compatible?

Given product review summaries (potentially with economic impact), can we improve ad generation?

Sentiment & Presidential Election

Political News and Prediction Markets

Hillary Clinton

http://data.intrade.com/graphing/jsp/closingPricesForm.jsp?tradeURL=https://www.intrade.com&contractId=177134


Hillary Clinton, Feb 2nd


Mitt Romney

http://data.intrade.com/graphing/jsp/closingPricesForm.jsp?tradeURL=https://www.intrade.com&contractId=175736


Mitt Romney, Feb 2nd

Summary

• We can quantify unstructured, qualitative data. We need:

• A context in which content is influential and not redundant (experiential content for instance)

• A measurable economic variable: price (premium), demand, cost, customer satisfaction, process cycle time

• Methods for structuring unstructured content

• Methods for aggregating the variables in a business context-aware manner

Question:

• What needs to be done for other types of USG?– Structuring: Opinions are expressed in many ways

– Independent summaries: Not all scenarios have associated economic outcomes, or difficult to measure (e.g., discussion about product pre-announcement)

– Personalization: The weight of the opinion of each person varies (interesting future direction!)

– Data collection: Rarely evaluations are in one place

Documents

Prof. Panos Ipeirotis Search and the New Economy Session 5 Mining User-Generated Content