Today, Google has reaffirmed that 15% of its searches done by users on a regular basis has never been seen before. They stated this in 2013 and have restated this metric after Project Owl was announced today. Google stated:-
There are trillions of searches on Google every year. In fact, 15 percent of searches we see every day are new — which means there’s always more work for us to do to present people with the best answers to their queries from a wide variety of legitimate sources. While our search results will never be perfect, we’re as committed as always to preserving your trust and to ensuring our products continue to be useful for everyone.