Using data from 5 websites, I calculated the percent of total keywords (not total traffic) that showed up as “(not provided)”, first between the dates of Oct. 17-31 and then between Nov. 1-14. The below chart shows the results:
The average appearance of “(not provided)” between Oct. 17-31 was 2.13%. The average appearance between Nov. 1-14 was 20.06%, making the average percent increase 1074%.
This information more or less agrees with Search Engine Land’s findings.
The question is: What does this mean for SEO? It means that we won’t be able to see information about (based on my results) 10-40% of our keyword searches, the searches coming from those who are most likely the most internet savvy (as they spend enough time online to sign up for Google). It should be noted that the highest increase in the appearance of “(not provided)” came from my own site, which is heavily focused on bringing traffic in via keywords. Whether this means that people interested in SEO, either SEOs themselves or people seeking SEO services, are more likely to have Google accounts (and I suspect that SEOs especially are more likely to be signed in to Google) and are therefore more internet savvy, I cannot say. I don’t think this change greatly affects how SEO should be performed, but I do think it could have serious effects on keyword research, especially if the Google Adwords Keywords tool no longer takes into account keyword searches conducted by logged in users.
In addition, this change can significantly affect conversion calculations. This is essentially what’s happening: Say you own a clothing store and are working behind the counter. You blink your eyes and suddenly a T-shirt is missing off the rack and the money to pay for it is on the counter. You have no idea who purchased the T-shirt, no idea what demographic they fall into, no idea what brought them to your store in the first place. You’ve made the money and that’s great, but you don’t know how to attract more people like this paying customer because you have no idea who they were.