Knowing an item's sales rank gives an indication of how it's selling right now. Tracking that rank over time gives an indication of how its sales are changing.
Sales rank is a look at how a particular item is selling in relation to every other item. An item with a sales rank of 1 is the best-selling item at Amazon right now. The lower the number, the better the sales.
One problem with the sales rank number is that it's only a snapshot of the last 24 hours of sales data. There's no indication of the way sales have changed over periods of time for any particular item. Luckily, there's an application that can help out.
JungleScan (http://www.junglescan.com) tracks any item at Amazon and charts the progress of its sales rank over time. The front page includes those items with the biggest changes for the day (both good and bad), much like a stock report.
If you're interested only in certain products rather than general trends, you can add items to your JungleScan profile. Click on "your portfolio" and create an account if you don't already have one.
Once logged in, you need to add items that you'd like to track. The quickest way to add products to your portfolio is to click "track new item" on the top menu. In a new browser window, visit Amazon.com and find the item you're interested in. Browse to its product detail page and copy the URL; then go back to JungleScan and paste in the URL. If the item has a sales rank, you'll have the option to "Save this product into your personal AmazonScan portfolio." Continue adding products until you've assembled a list of those you're interested in. Figure 3-9 shows a JungleScan Portfolio tracking six items.
On the portfolio page, you'll see the time that JungleScan began tracking the item, its title, and its current sales rank. The rank is updated roughly every 24 hours. Clicking the current rank takes you to the product details, as shown for Google Hacks in Figure 3-10.
The details page provides a look at how the sales rank has changed over time, along with a nifty graph to give a visual sense of its movement. You can adjust the graph to show different time periods, or even zero in on the raw data used to generate the graph.