In 2011, the aggregate required for an ATAR of 98 was 432/500. (Just a random choice of ATAR)
So to get 98, you needed to average a scaled mark of 43.2/50 per unit, or 86.4% per 2 unit subject.
So here is the ranking of subjects based on the percentage of the candidature who beat that scaled mark in 2011:
Maths X1: 34
English X1: 13
English Adv: 9
Economics: 9
Maths 2U: 8
Physics: 8
Chemistry: 8
Modern History: 5
Biology: 4
Choosing a different target ATAR would change the rankings slightly.
For an ATAR of 95, the corresponding percentiles are:
Maths X1: 53
English X1: 28
Economics: 19
English Adv: 18
Chemistry: 18
Maths 2U: 17
Physics: 17
Modern History: 10
Biology: 9
So those 5 subject in the middle are almost indistinguishable.