Seeing as the UAI is a rank, i think it must mean that alot more people are scoring higher marks in their HSC then in previous years.
If i did my HSC in 2001, and got the same marks i got in 2003, i would of got 97 UAI according to the SAM program, which is 4 UAI points higher then what i got this year.
I guess this could also mean the tests are getting easier.
But seriously, i have no clue, im just guesssing here. I don't understand much of how any of this is calculated. If you ask me it seems very very complicated. But Laz must understand it as he made his prediction program so acurate, so ask him.