Marcos Benevides’ Slideshare PPT has been floating around for over a year now. It’s a powerful illustration of how unknown words affect reading fluency (speed + accuracy), especially for anyone who thinks students will be OK reading anything that’s less than 98% comprehensible.
Still, the syntactical clues in Marcos’ PPT helped native speakers. In order to simulate a student’s reading experience more accurately, I removed those clues. Here’s the result (download, here, for sharing):