When Google revealed last October it would be making Secure Search the default for logged-in users, online marketers were rightly concerned but perhaps not quite concerned enough.

Our figures show that SSL accounts for much more than the 10% of search traffic Google initially estimated.

Whether it is an increase in the use of Chrome (whose users also have SSL as default) or the impact of Google+ in encouraging more users to be logged in, a technology test on our own site tells us that 23% of search traffic coming to the site is secure, meaning the referral natural search terms are hidden in nearly a quarter of site visits.

In October, the industry soon spotted that, while, yes, Google could argue that SSL as default was a step towards increased user privacy – currently a key issue across markets – it would also, conveniently, encourage more paid search spend since marketers could still tell which paid terms were driving traffic and would lose some of that insight in SEO.

We don’t have figures for that shift, though it will be interesting to dig into Google’s first quarter results to look for a trend, but what we do know is that, on our own site at least, much more than the 10% Google identified last October, is secure.

Our fix uses the same technology we use to identify the search terms used by visiting users as part of path-to-conversion reporting. But, instead of revealing these terms for SSL searchers (since they are hidden), it instead identifies the visit as coming from a secure search and collates that data to reveal secure search share.

This data is useful to marketers to at least understand the volume of search traffic coming from SSL and retain some insight on the value that SEO is delivering, as well as provide some context for the insight they gain from non-SSL data.

The figures are bound to look different across companies and sectors. TagMan doesn’t put much into paid search and so the bulk of search traffic is from organic listings and we don’t have figures for pre-SSL to understand what it looked like before to gauge a trend.

But, even for those businesses at the hard edge of search – financial services, retail, travel – where paid search accounts for a much greater share of traffic, transparency to drive efficiency is a critical issue.

That the drivers of a greater share of their search traffic is hidden from them ought to be a major concern, especially as Google has now begun to encrypt UK search referral data.