Also they don't record personal data, so it's actually number of arrivals, not tourists – i.e. each time you come to stay, it's counted separately: 1 visit for 5 days = one tourist, 5 visits for 1 day each = 5 tourists.
Spain is pretty high because there are loads of charter and group holidays arranged to i.e. Canary Islands from Sweden. I'd say majority of those who travel to Spain either go to Barcelona or La Palma, Majorca or Tenerife (or some other major island). It's often the cheapest choice if you're looking to sunbathe and swim :P