Have you ever noticed CSI mentioned at the bottom of Yahoo! Finance pages as the supplier of historical data? From my experience, I can state confidently that CSI has the cleanest data available, which is probably why they have a relationship with one of the most popular financial websites. Commodity Systems, Inc. (CSI), supplies a broad spectrum of financial end-of-day data in their product, Unfair Advantage (UA). UAís strength lies in the quality of the data it delivers and its ability to manipulate that data.
The initial data (compressed) and the program software come on CD. After installation you use the Internet to update the CDís data to the present date, as
well as for daily updates. CSI covers data from more than 80 world exchanges. The data remains compressed until you request specific files to be built.