It's interesting I found this article:
http://www.tvtonight.com.au/2008/07/nrl-footy-show-slipping.html
This article is from July 2008. Interesting to note that only as recently as 3 yrs ago (March 2008), it was averaging 271000 viewers in Sydney, nearly triple what it got last night. At the start of this year, I thought to myself that they would be lucky to crack 200000, but given what happened last night, 100000 could be a struggle.
I know that probably no one has any articles or records of what the ratings were like many years before that, but I assume that they were even a lot higher than 271000, which makes the 98000 from last night (in the 9:30pm timeslot) look very bad. It probably has resulted in a huge decrease in the amount of ad revenue Ch9 used to get in that timeslot.
Regarding the decline in ratings, the first time I remember that they were in trouble was in 2005 (when Ch9 tried to call in Ray Hadley and Rebecca Wilson). This may have been the beginning of the 'downward-spiral', but I was just interested to know when the ratings were at their peak