Quote from sheridan:
Could you give me an URL for one of the services that you think offer good ED spread charts?
A no-frills free site model is at www.britefutures.com
www.barchart.com - the Advanced Commodities product - offers more functionality and history for US$20 p.m. They also provide Time, Price and Size stats for traded spreads There is an example of their spread charts at the 'Sample Site', plus one posted.
FutureSource also used to offer spread charting capability with their free 'premium' chart product.
Putting myself in your shoes, I'd be looking to reconcile the wishlists in this thread with the objective and target market for your site. It appears that volume at price is your USP, and I wonder how relevant this is to many ED traders, who are primarily spreaders. Also, how meaningful is volume-at-price in a market which contains significant hedging activity.
