From my experience the same scaled scores have been becoming lower percentiles in math, and the oposite in verbal.
For instance, a Q47 is the 76th percentile (when it used to be 80%) and V41 is 92nd when it used to be 90th. Now, I'm thinking that since the GMAT is rapidly growing in countries such as India and China (non native english speaking countries) that the quant section is becoming more competative and the verbal is becoming less competative. THis is why your verbal scaled score can really help drive your score higher.
As far as the algo goes with your overall score, that is anyone's guess! But generally, it seems those have been getting a little more competative too. For instance 750 used to be 99th percentile, now it's 98th. SO there must be a higher precentage of people getting in that high range.
I would love to crunch the numbers on the GMAC database, I would get a ton of enjoyment out of knowing how it all really works. It's really anyone's guess
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