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In Open Site Explorer I can see that the www and non www versions of my site gets treated differently with one group of links pointing to each version of the same page. This gives a different PA score. eg. http://mydomain.com DA 38 PA 37 http://www.mydomain.com DA 28 PA 27. Currently our preferred variation is https://www.mydomain.com but it used o be http://mydomain.com for 3+ years and I can see that the non www version of my domain have more authority. Would you advise us to "change back" to setting our preferred url as the non www version as before or would it have a negative impact on our SERP ranking etc if we change it again now?