I have changed the permalink structure for a website containing about 2000 URLs. The old urls are 301 redirected to the new ones.
Google indexed most of them yet they show as duplicate titles in webmasters tools.
The thing is that after I changed the permalink structure I also changed the Title structure. So considering the fact that google sees the NEW title structure for the old urls it clearly shows that they were re-crawled, but instead of de-indexing them, they are shown in webmasters tools with a notice saying they are duplicate pages of the new ones.
Any idea why this happens ?
I would have expected the new permalinks to replace the old ones and for Google to NOT keep the old ones in the index too and consider them duplicates.