I finally sold my copy of Simon and Blume’s Mathematics for Economists that has been left unused for the past 4 years. Fortunately, unlike undergraduate textbook, graduate textbook tend not to be updated at the same ridiculously pace and so the resale value is still moderately high.
Camelcamelcamel.com is a service that helps users monitor prices of products on Amazon and alerts users by email, twitter, or RSS when prices change. I have used it as a buyer for a few things before, but never for books and never or selling. As a seller, I was curious about the history of the listing price for Simon and Blume and camelcamelcamel ends up being useful as well. I believe camelcamelcamel earns money from Amazon by referring customers to them and perhaps sell the threshold data from the users to companies. They have sites for Best Buy (http://camelbuy.com/), Newegg.com (http://camelegg.com/), and a few others.
The reservation price data from potential customer is worth money for businesses, and from an economic point of view it is data that I would love to analyze comb through and analyze. This should help with understanding how consumer behaviors change over this past recession. This also in some sense ties back to projects like "Billion dollar project," a movement to use more real time data to analyze the macro economy.
Anyhow, now that I am done with the pedantic diatribe, here is the chart of the data for Simon and Blume. A few things to keep in mind when looking at this chart:
- How to read the chart:
- The green line is the Amazon selling price.
- The red line is the "3rd party" used book price. My book listing would fall under this group.
- Caveats about the chart
- Note that these are plots of the lowest listing price and not transacted prices. In other words, a data point of $71 in November 15, 2008, means that the lowest price book on that day is listed for $71. It is possible that no one ever bought the book at that price.
- Note the asymmetry are likely caused by different factors.
- The movement up can be attributed to a buyer purchasing a book and so the listing price increase.
- The movement down is likely to be attributed to sellers adjusting its listing prices. Either due to their own inventory increase, new entrants under cutting the existing lowest price, or other sellers responding to other seller's prices.
- Some observations
- I do see some run up in prices during the summers. The book price seems to have peaked near $71 in August 2010, and peaked near $110 around August 2011. Given that this is a textbook used by for entry level "math for economist" class, this makes sense. However, it is unclear to me why the listing price has gone up so much this past year relative to the previous 2 years.
- The Amazon prices are very stable. And it doesn't have the seasonal pattern like that of the 3rd party used books.
- In the used book market, the frequency of the update has increased since April 2011. There are many possible causes:
- a technology issue on the part of camelcamelcamel on checking and updating prices
- someone (Amazon or another company) has developed a system and the software to allow sellers to update their prices based on either their own inventory or on other people's prices.
- The variance of the book prices has increased. So when a buyer buy a book, the next lowest price book is in a sufficiently different price range and so we see a fluctuation. (In other words, if two books are being sold for $61. After 1 book got purchased, the lowest listing price is still $61. If books are all listed at different prices, then after someone purchased a book, the lowest listing price will change)