Daniel_Zar wrote:"5000 words allow you to understand about 98% of most ordinary texts" is an overestimation.
The mistaken assumption is: since those 5000 words make up 98% of a given text, knowing those words I'll get 98% of the text.
In reality it is more around 80%, and I may be optimistic. As someone pointed out, the 2% you don't know is much heavier in terms of meaning.
Here's my N=1 experiment. I just finished reading Musso's Demain. I had about 1100 unknown words there. The novel is about 88k words, that means that for comfortable reading I could theoretically have 1760 unknown words (2%). Well, I had less than that but still I wouldn't say that my reading would be uncomfortable without pop-up dictionary. Also, initially I sped through the second half of the book (I really wanted to know the end of the story) by reading and listening the audiobook at 1,5 speed (so I would cut even the idea of using a dictionary). I could still understand the gist of the story although in a couple of scenes the details were unclear to me. Still I wouldn't describe such level of comprehension as comfortable. For comparison, when I read a fiction book in English (of the same size) I tend to have 300-500 unknown words and in that case I feel pretty comfortable. So, I would venture to say that 99.5% is the right percentage for comfortable reading. (and, I guess, I don't need to remind that getting from 98 to 99.5 is a looong road:Link)