It doesn't even have to link the results to a specific user, linking them to the search terms is enough. It's possible to achieve something similar by measurin

It doesn't even have to link the results to a specific user, linking them to the search terms is enough. It's possible to achieve something similar by measuring bounce rate, but in any case, the sheer number of searches is what matters. For new entrants, this kind of expertise will be very hard to get.