An average person, not the average person. They'll at very least target the content by country, and if you have a fixed or rarely varying IP address (which I do at home, and may public wireless APs do in my experience) they can be more fine-grained than that and give recommendations based on what people in your more local area have searched for recently.

I had an Italian friend staying in my spare room for about half a year some time ago (hassles with previous landlord, took her and her fellow a while to save to the point where they could afford a place together). For many months afterwards I would get Italian language recommendations and adverts from youtube and others, even in incognito on a fresh device.