Citations & context? Your numbers seem unrealistic, Google does not operate 90% of email accounts. Search is definitely seeing erosion courtesy of competitors that have gotten more competent and numerous in the last few years.
> does not operate 90% of email accounts
I said private email accounts.
I am looking. What I see is it being devoured by Google. Search 99%, Chrome 80%, private email 90%, Google accounts for work, for school kids, and Google Analytics tracking in every web site.