Participatory Sensing in Commerce: Using Mobile
Camera Phones to Track Market Price Dispersion
, Chun Tung Chou
, Salil Kanhere
, Yifei Dong
, Shitiz Sehgal
, David Sullivan
Computer Science Department, Portland State University, Portland, OR 97207, USA
School of Computer Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
salilk, ydong, shitiz.sehgal, dsul945, firstname.lastname@example.org
In economics, price dispersion refers to the price difference of a homogeneous good across different vendors.
According to  “The empirical evidence suggests that price dispersion in both online and offline markets is sizeable,
pervasive, and persistent.”
Not surprisingly, there exist several popular web commerce sites such as Froogle that
enable users to track consumer pricing information in online markets. In this paper, we present and explore our vision
that participatory sensing can be employed in this new application domain to track price dispersion in homogeneous
consumer goods even in offline markets. We discuss two proof-of-concept participatory mobile camera-phone sensing
systems that we have built: (1) automating fuel price collection, and (2) semi-automated scanning of receipts.
Price dispersion of
goods is a fact of life . We emphasize homogeneity because if two goods
are not homogeneous, such as televisions of different brands, then there is a quality difference which makes them
hard to compare quantitatively.
We have encountered myriad real life examples of price dispersion. For example,
the following homogeneous goods were sold at different stores at fairly different prices at the same time in June
2008. We observed a $10 price difference for multivitamins (a $30 product) between Costco and RiteAid stores,
and nearly a $200 price difference for HDTVs (a $2000 product) between Circuit City and Best Buy. Online, the
quoted air fare for the same flight was $600 higher at Expedia than Lufthansa $2600 at the same instant of time.
Price dispersion is attributed to several causes. A seminal article by Varian  suggests that price dispersion
might be a deliberate marketing ploy by retailers to entice consumers into exploring their choices. Nevertheless, a
major cause is the consumer search cost incurred in collecting pricing information from competing retailers,
including the opportunity cost in time in acquiring this information [Baye06]. Price dispersion remains widely
prevalent on the Internet (15-17%) , although studies have speculated that the low Internet search cost, where
alternate retailers are often just a mouse click away, will eliminate price dispersion . Not surprisingly,
numerous web commerce sites such as Shopzilla
try to remedy this situation in online markets by
providing a clearinghouse of price information for a homogeneous good for different e-retailers.
There are compelling reasons for creating such a clearinghouse of up-to-date product pricing information, even