Inter-viewing the Amazon
Web Salespersons:
Trends, Complementarities
and Competition
Michalis Vafopoulos
(with T. Theodoridis & D. Kontokostas )
vafopoulos.org
2/10/2011
Main issue
Identify purchasing patterns in Web retail
using available public data
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outline
① Before analysis
② Data
③ Innovations
④ Main results
⑤The Amazon co-purchasing network
⑥Amazon: the book-based multi-store
⑦Triad analysis: Winners in Product wars
⑧Switching to best sellers
⑨Hidden complementarity saves MS
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Before analysis
 Why Amazon? the best proxy for Web retail
 Algorithms: item-based top-N recommendations
 Analysis? co-purchase directed graph
 related literature?
 Computer science (Collaborative filters, Karypis)
 Economics (market basket analysis, Oestreicher-Singer)
 Software? Gephi, iGraph, FANMOD, mysql, & xls (old
habits!)
Data
 226,238 items
 13,351,147 co-purchase connections
 The crawler was started with an initial set of 300
items, which were the top 10 selling products in each
of the thirty categories.
 61 recommendations per item (average)
 2nd level added 17,204 items
 3rd 208,740 items
Innovations
 Cross-category analysis
 Broad graph (in dyads at least one from category)
 Strict (both items from the same category)
 All recommended items crawled (max 104)
 Triads analysis
 Community analysis
Main results
 Amazon has evolved into a book-based multi-store with
strong cross-category connections.
 Top selling products are important in the co-purchase
network, acting as hubs, authorities & brokers.
 Co-purchase links not only manifest complementary
consumption, but also switching among competitive
products (e.g. Kaspersky -> Norton).
 competitive products consumed as complements
because of the existence of compatibility and
compatible products that facilitate their joint
consumption.
The Amazon co-purchasing network
Item X co-purchased
most frequently
with products Y1, Y2,..
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Amazon: the book-based multi-store
The Amazon copurchase network
for all item
categories
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Triad analysis: Winners in Product wars
Analysis shows that copurchase links not only
manifest complementary
consumption, but also
reveal competitive
relations among products
that are perfect
substitutes.
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Switching to best sellers
the case of Internet security market
Ass: if products A, B &
C are perfect
substitutes (authority
triad), then A has
higher sales rank
consumers who bought
Internet security s/w,
more often, also bought
Norton Internet Security
than related products
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hidden complementarity saves MS
MS (purple) & Apple
(orange) communities
are “mediated” by
compatibility like
VMware Fusion,
Parallels Desktop and
compatible products
like Office for Mac.
overview
①Amazon: the book-based multi-store
②Triad analysis: Winners in Product wars
③Switching to best sellers
④Hidden complementarity saves MS
Questions?
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supplement
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Descriptive statistics
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Amazon: the book-based multi-store
Figure shows the interconnections among all
different categories of products in the Amazon
co-purchase network.
A link from category A to category B is added if
products from category B are present in the
broad network of category A.
The link intensity grows with the number of
products that are present in that network and
the size of a category denotes the number of
products that belong to it.
The stronger links are from Movies & TV to
Books, from Kitchen & Dining to Books, from
Toys & Games to Books and from Books back to
Movies & TV.
The Amazon copurchase network
for all item
categories
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hidden complementarity saves MS
Fig. 2 shows a part of the Strict software co-purchase
network, where different colors indicate different
community membership. Different product communities
have been identified based on the spin glass community
detection algorithm and has been computed by the R
package iGraph. It is interesting to observe that
seemingly competitive products of Apple and Microsoft
are in reality consumed as if they were complementary.
Microsoft (nodes with red color) and Apple (nodes with
blue color) product communities are “mediated” by
compatibility like VMware Fusion, Parallels Desktop and
compatible products like Office for Mac.