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SEMRush.com can do this for you, but you need to upgrade to the Guru level to get access to historical data. It will give you the info for you and any competitor you want. The Guru level is about $149 a month. It doesn't require an annual or minimum commitment so you could join at that level for a month and drop back to free once you felt like you'd gotten the data you needed. Does that help?

Good discussion going on here! While I agree with the comments here that strong local businesses are still faring well in the SERPs, I, too, have noticed Google's bias towards Yelp and actually blogged about this recently. A few years ago, there was a similar situation going on with Merchant Circle. Practically every local search would bring up Merchant Circle listings, but it seems to me that MC has now been replaced by Yelp with similar results. I rarely see MC results on page one, but Yelp has become extremely dominant. This could change, of course, but for now, having a well-maintained Yelp profile is very important for most local businesses.

Yes, the resource is still correct. The 302 will pass none of the link juice, changing to a 301 will pass most of the link juice (90%+).

I think in the future it will affect your general domain ranking a little bit (Seems like a logical step for google?). But just as Ryan says presently it doesn't seem to affect it.