Google Toolbar Page Rank (GTPR) will most likely not get update any more according to google
[webmasterworld.com]. Whilst this was of limited use, due to its slow update and limited 1 - 10 scale, there remains huge merits in being able to quickly evaluate the "worth" of a page or site.
So what other tools can you use for this?
Way back in May 2012 I published some research showing correlations between PageRank and the popular metrics from Moz and Majestic. Three metrics correlated well:
1: Domain Authority (0.787 correlation)
2: Trust Flow (.746 correlation)
3: Citation Flow (.814 correlation)
In the comments, further research from Rand's team showed
4: mozTrust correlate at 0.66
5: Page Authority correlate at 0.68 Why Page Rank is not as good as Trust Flow or Page Authority as a Quality indicator
Citation Flow correlated better than Trust Flow in my test because, I believe, both calculations start with an absolute value for each web page, based in Google's case on link counts according to the original PageRank paper (I am happy be corrected) and in Majestic's case on either IP counts or domain counts (I forget which now). In other words - modern self replicating systems can inflate these counts artificially. Because Trust Flow uses similar methodology, but weights counts based on their proximity to known trusted sites, Trust Flow is less prone to artificial manipulation - although Google obviously have their own less public ways to avoid manipulation. Page Authority also effectively does a similar "proximity to trust" algorithm, but using an entirely different methodology as it is based on Moz's ranking data... A site is trusted by search engines, Ergo it is trusted in Page Authority. (This is a methodology Majestic cannot replicate as Majestic has never been involved in rank checking). Moving to 2014
Over the intervening years, I have been getting periodic notifications from a friend on the correlations with Page Rank, though often with limited sample sizes. If you want the strongest correlation with Page Rank, then Citation Flow looked to be the best back then, but more recently things have changed with Trust Flow being closer in more recent tests, but if you want the strongest metric of QUALITY then I think you should look at Trust Flow or Page Authority.
Here are some newer correlation tests on a smaller data sample:
Ahrefs DR: 76.32%
Trust Flow: 72.79%
Citation Flow: 70.99%
Webmeup: 97.03% - This last one looks SO close to PageRank that I can only assume the metric largely IS PageRank taken from the GPTB itself. If that is the case, then you can expect that correlation to deteriorate pretty quickly now that the data is not being updated.
I should point out on this last table that the sites analysed were all "Fairly decent" sites in a narrow vertical. I have noticed that the different metrics on offer react very differently to "outliers" - sites that are either very good or very poor. The original sample was quite a few sites but (importantly I think) generated randomly for the purposes of the test.