To reduce the search engine rankings of low-quality sites, Google announced a new update 'Panda' on Feb 24, 2011 in Google US. The change impacts approx 12% of search queries. It is rolled out globally on April 14, 2011 to all English-language Google users.

I see Google search engine traffic comes from US increases after Feb 24 in Google Analytics.

Now, It is near to double. See following weekly graph:

How To Check Google Panda Effect

If you want to check Google Panda algo effect on your site, Login to Google analytics.

Go to Traffic Sources >> Search Engine

Click Google

Expand "Keyword" drop-down and select "Country/Territory" option in Grid Header.

Enter "United States" in Filter below the grid.

You will get traffic comes from US. After April 14, No need to filter by US.

Share your thought about this new panda algo in the below comment box.

Enjoy Google!!!