The intro background briefings provided at the start of each episode could easily have contributed to the ratings increase.
They are there to help the audience get the most out of the show to assist to capture and retain viewers. Survivor requires a decent scope of knowledge to derive full viewing pleasure... high commitent viewing. Plenty of people probably can't be bothered to make the effort after a long day working, and want oven ready fries without too much effort or thought.
Hmmmm. The ratings data is based on about 5,000 households...representing about 8.4+ million hh / 24+ million pop.....pressumably statistically reliable when extrapolated (without checking). Not to mention OzTam's self-interested/independant (yep same breath) ownership and oversight, lol.