The latest QS Top Universities Rankings have six Australian institutions in the top 100, ranked: 31 ANU, 40 Sydney, 41 Melbourne, 44 NSW, 46 Queensland, 55 Monash, and 92 UWA. These results are similar to other ranking schemes, are widely reported, and influence student choices. However, the relevance of the methodologies used is questionable.
The QS rankings are based on five indicators: Academic and Employer Reputation, Faculty/Student Ratio, Citations per faculty, International Faculty and Student Ratios. Reputation makes up half of the raking, but is, in part, a self fulfilling prophesy: academics and employers base their ranking of an institution, in part, on how universities have ranked in the past. The ratio of teachers to students might seem more objective, but this doesn't take into account if these teachers are qualified to teach (most university academics do not have a degree in education). Citations provide some measure of research output, but this may indicate less interest by the staff in teaching. International staff and student ratio is used as a proxy for soft skills, but does not measure if the international staff and students mix, or are confined to specific campuses and classes.
Another difficulty with QS and similar ranking systems is that they only cover about one tenth of higher education institutions in the world. Most students can't afford to attend one of these "top" 1,000 universities. Most students would be better off with an institution not in the top 1,000, but which focuses on quality teaching for skills in demand, rather than research. The Webometrics Ranking of World Universites, tries to provide a boarder ranking, and covers more institutions.