Difference search result for BING API vs BING.COM

Anyone know why the search result for normal bing.com and bing api 2.2 is different?

Example:

http://api.search开发者_StackOverflow中文版.live.net/xml.aspx?Appid=yourid&query=aggregate+study+site%3Awww.sandag.org&sources=web

and

http://www.bing.com/search?q=aggregate+study+site%3Awww.sandag.org

Returns completely different results.

It is the market parameter. Check it. Bing specifies the market parameter based on your IP , and your cookies and browsing history.