Japanese ratings call Prius world's most efficient car, 89.4 mpg (US)! — Autoblog Green
So the ~50mpg prius gets a MPG rating of 89mpg in Japan, just for a comparison, so I would guess that a Yaris like this would only get a USA EPA raiting of 45mpg or so, but that is still much better then pretty much any other non hybrid car that is on the market right now.