Say, if the old domain was xyz.com, and the new one is abc.com, we 301 redirected every url from the old site to the new. So for example, xyz.com/post1 now redirects to abc.com/post1.

Does that help?

We look at the old domain's Google Analytic account. All traffic to the new domain is shown there.

My Client had a site that ranked for a pretty competitive two word phrase, but for a variety of reasons had to transfer the site to a different domain name (with none of the previous keywords). We've 301'd everything just fine to the new site, but our traffic for that two word phrase, as well as related long tail traffic, is beginning to drop.

Could the drop be related to something that we didn't do well in the transfer? Or is it due to the new domain name now not being an exact match?

Sitenote question: Our Google Analytics is still set up for the former domain name and shows data just fine. Is there any reason to switch GA to the new domain? What are the pros/cons?

Much thanks in advance!