Price Median Info
Price Median Documentation
The price median static files are generated daily based on all prices I have in my database. Prices are always at least 24 hours old due to my usage of the daily dump files from Eve-Central - the prices may be as old as 48 hours depending on when you download my static files.
Additionally, at the time of this writing, my medians are based on all prices in my database (prices going back to 2007-11-13). Until I have implemented a date filter as well, prices will be very slow to reflect any quick fluctuations.
A couple notes about median calculation: my raw price table contains an entry for unique price seen, i.e., if a single player posts a sell order then changes the price of that sell order once before the order is complete, each of those prices are part of the set of prices that I use to find the median from.
The median calculation is done by simply selecting the count of orders in the raw price table for a certain type and whether that order is a sell or buy. With that count, I pull the middle order of those selected ordered by the price on the order.
Usefulness of Data
Trying to use one single number to represent some information about items in EVE is difficult to do at best. I provide a lot of prices and choosing the one that best suits your application is pretty important. In general, buy medians will probably be lower than the amount you would actually get if you sold the good as a buy order. Similarly, the sell median price will likely be somewhat higher than the price you would pay if you were to buy an item. I have generally been listing both prices or providing a method to choose which price a user wants to use in my own applications that use these prices.
Additionally, you can provide a regional selection of medians if you know your application will target a specific region or users of your application will want that information.
If you want a single price to estimate the value of an item, for example, a killboard, you would probably want to use The Forge region’s sell medians. These prices are generally held as the index to use for item pricing.