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I've been thinking about the subject and I've always wondered, from where do they obtain the data that is analized in applications, I've looked at Nasdaq's website and they do not seem to have any sort of APIs, do the firms parse yahoo's finance section, or are there special contracts, agreements in places with the different stock markets?

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closed as off topic by S.Robins, World Engineer, gnat, chrisaycock, Walter May 25 '12 at 12:16

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This might be on topic on the Money site or maybe on Cross-Validated. –  World Engineer May 25 '12 at 4:48
    
Yeah, I was unsure as were to post it but I ask with a programming interest if you can call it like that, if it needs to be migrated I'd have no problem at all. –  Triztian May 25 '12 at 5:05
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3 Answers

There are firms that specialize in providing Market Data for most asset classes. Reuters, Bloomberg and Markit are three of many. The data is sold, so there likely won't be public APIs for most of it. Academics use CRSP to track stock returns - most of the data on efficient markets is from that data set.

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Yahoo does have a simple API for obtaining current data for individual stocks. Details here:

http://www.gummy-stuff.org/Yahoo-data.htm

But it's not a way to get historic data. For that, you'll probably have to subscribe to a service.

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They subscribe to data feeds to the various exchanges and record the data as it comes in. Free sources like Yahoo and Google can have errors in the data, can be delayed, and don't have all the information that professional traders require.

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