Why there is rank difference of site in Google.com & Google with other extension

[seomixi]

I am not able to understand that why there is a difference in position of my website with same keywords in google.com and google.ca or google.ca. On google.com my site is at 7th position with a keyword and with that same keyword it is at 5th page in google.ca. Can anyone here tell me the reason please? Your answers and experiences are most welcome, so please share.

[qr8gul1]

Because there is difference in the data center from different countries and the entire world.

The .com is international while the .ca is merely those in Canada.

[BETTY2010]

Yes, Search engine rank varies on data center.