How many people logged in Google visit your website by heykhend

Google announced they are going to switch to https:// logged-in people doing a search on http://www.google.com/, consequently their will be no more search query in the referrer for these people. It should not affect logged-in people doing search on http://www.google.LOCAL_TLD like google.fr/google.de…
I see on twitter people asking how much is the part of these google-logged visitors to mesure the impact of this change. Guess what ? Everybody can now how much logged-in-google user visit your website.
Actually, when a logued-in-google visitor arrive on your site from a google search he will have a special parameter « sig2=XXXX » in the referrer, a parameter a not-logged user won’t have. This parameter is leaked by the « www.google.XXX/url?sa= » URL which is reponsible to track the click in the SERP.
So by running this simple command on your apache logs, you can have an approximation of the part of logged-in-goolge visitor you have:

# this will grab all the google referrer "/url?sa=" you have in your log, and make it unique based on IP
egrep "www.google.[a-z.]+/url\?sa=" access.log | sort -k 1,2 -u > /tmp/google-urlsa-referrer.txt

# display the amount of logged people AND coming from google.com (and not google.fr/de/other-tld)
egrep 'google.com/url\?sa[^"]+sig2' /tmp/google-urlsa-referrer.txt | wc -l

# display the amount of all the people coming from google/url?sa (all TLD)
wc -l /tmp/google-urlsa-referrer.txt

Beware, this is just an approximation because it will only count among the users who have Javascript enable on Google (required to go to the « google/url?sa= » URL) and does not count people coming with strange google referrer. These URL where I can’t determine if the visitor is logged in google are like (it’s 50% of all google referrer):
http://www.google.com/search?q=query&… (no js)
http://www.google.com/webhp?sourceid=navclient&ie=UTF-8 (no js)
http://www.google.com/cse?cx= (sponsored search, assume not logged)
http://www.google.com/#.. (what the fuck, it’s extremly log ratio, no impact)
But, in my opinion we can consider the ratio of logged-in ratio from « /url?sa » referrer is the same for others google referrers. Or if you’re not OK with this assertion, you can consider they’re not logged in Google and recalc the ratio.
It’ is sure that you won’t have the same ratio of logged-in-google visitor on a IT/tech website and on a « how to loss weight » website. SEL reported that Matt Cutt said it will only affect a single digit of your user, I confirm BUT :
If Google decides to encrypt the search of all logged-in user (so including people doing search on http://www.google.fr/ and so) the stats would be totally differents, you could except something between 20-40% of your google traffic, but I repeat, now it should only affect google.com domain, but maybe latter… To check that you do :

# Amount of logged-in people coming from google, all google TLD included.
egrep 'google.[a-z.]+/url\?sa[^"]+sig2' /tmp/google-urlsa-referrer.txt | wc -l

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