I measured it with the first two reading speed websites that came up on my google search here and here. My reading speed was also tested when I was 16, with very similar results.
My comprehension is very good (in the 80-90% range) at the upper end for anything I can visualize, or when the details of the sentence do not change the meaning. For example, my comprehension would be very high for an action scene in a novel, but when I have tried to read that quickly about any non-familiar technical topic, my comprehension has fallen to the 20-50% range.
I did nothing to increase my speed. I learned to read at a very late age, and became able to read over the course of approximately 20 minutes (it was quite possibly one of the weirdest experiences of my life), and after that 20 minutes passed I could with far above-average adult speed. If anyone else has ever had this experience, I would love to hear about it.
http://en.wikipedia.org/wiki/Subvocalization
I'm curious about how often or to what degree visitors to this site subvocalize as they read. I was originally interested in reducing subvocalizations as a way to increase reading speed, as the idea is mentioned in multiple pieces I've read about speed reading.
The Wikipedia entry seems to focus on subtle throat and muscle movements, but I'm more interested to know if you "say" or "hear" the words in your head as you read.
Since reading about subvocalization recently, I seem to notice that I "say/hear" what I'm reading quite frequently. I'm not sure if this is causal (in the way that the command "don't think of pink elephants" obliges you to do so), or if I just notice it more now, or both.
When I'm very engrossed in a book either I don't notice the subvocalizations or they stop happening, so seems that it could either be a cause or a symptom of distractedness.
In the comments, please describe your mental subvocalizations (or lack of them) and if they are related to how engrossed you are in the book. Any other comments relevant comments about speed reading or subvocalizations are welcome.