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We have a long-time previously well-established website that was hit by panda. On one section of the site, we have dynamic urls that include %20 in them (e.g. North%20America). It's recently come to our attention that google has both a version of the url with a plus sign (+) and the version with the %20 (space) (e.g. North+America). Upon researching this, it seems that a hyphen (-) is preferable to either of the above. We obviously need to remove the %20's from the urls as they can cause issues. So, should we stick with the + sign since it's already indexed and ranking or do a 301 rewrite and change them all to hyphens instead of the plus sign? This is the one section of the site that has maintained rankings through the panda debacle, so we need to take that into consideration as we don’t want to lose the rankings that we have. Along the same lines, we have two other sections of the site that provide search results as well, though these are all formatted to use a plus sign. Is it advisable to do a 301 rewrite to change the plus signs to hyphens on these as well or just leave them alone? This particular section has lost rankings over the last year with panda updates.

We're trying to find out  what percentage of words in a page title need to be the same for it to be considered duplicate? We have search results pages for each country on our site, so the only difference in the page title is the country name and they are all being flagged as duplicate, even though they are not 100% duplicate.