If you are using blogger platform for your blog and not using any custom domain service, you must have noticed your blog being redirected to country specific domain. If you are from India, you [blogname].blogspot.com will be redirected to [blogname].blogspot.in
Well, if your site was earlier visited through .com 20 times a day, it may now be visited with .in 10 times and .com 10 times distributing your alexa ranking to 2 different domains resulting in loss of your alexa ranking.
See the below 2 images as a example ..
You yourself can check that for .com, .in, .co.uk, or any other domain. They are all different.