Australian institutions performed well for their academic reputation and international student ratios in the QS World University Rankings. Most, however, were at the bottom of the list of 1000 universities for their staff-to-student ratio.

Australian National University is the country's top-ranked institution in equal 29th place, a small fall from 24th last year. It was followed by the University of Melbourne in 38th place, the University of Sydney, 42, and the University of NSW, 43.

The University of Queensland, at 47, Monash University, 58, and the University of Western Australia, 86, have also appeared in the top 100.

Overall, Massachusetts Institute of Technology is the top-ranked university in the world for the eighth consecutive year, followed by Stanford, Harvard, Oxford and the California Institute of Technology.

The QS World University Rankings is an annual publication by Quacquarelli Symonds (QS). Previously known as Times Higher Education-QS World University Rankings, the publisher had collaborated with Times Higher Education (THE) magazine to publish its international league tables.

The rankings measure a university's academic reputation, graduate employability, student-to-staff ratio, research performance and international student ratio.

Two-thirds of Australian universities improved their overall performance in this year's rankings. But 31 of the country's 35 institutions went backwards in the staff-to-student ratio measure, which the ranking's compilers described as "a proxy for teaching capacity".

Many, including UNSW, Monash, the University of Western Australia, the University of Technology Sydney and the University of Wollongong received the aggregate bottom ranking of "601+" on this measure.

At the same time, Australian universities have bucked a declining trend among US and UK institutions in the international student ratio measure, with 26 or Australia's 35 universities recording an increase in the proportion of overseas students.

Sydney University, Melbourne University, Monash and ANU have all ranked particularly well for internationalisation, with global ranks of 20, 23, 27 and 30 respectively for this measure.

"The influx of international students has coincided with significant and near-uniform drops in our faculty/student ratio indicator," QS's director of research Ben Sowter said.

"It is imperative that Australia endeavours to continue expanding its teaching capacity to meet demand that is likely to continue increasing."

There were more than 550,000 international students studying in Australia last year, with the majority at higher education institutions, according to Universities Australia.

However, the growing reliance of some of Australia's biggest universities on income from international students has raised concerns about the consequences of any decline in international student numbers.

Australian universities also performed well in the academic reputation measure, which is a compilation of the responses of 94,000 academics from around the world, with Melbourne University the best-ranked at 15, followed by Sydney university at 25 and ANU at 29.

The employer reputation measure, based on 44,000 employers' responses on each institution's link to graduate employability, was more varied, with Melbourne University, Sydney University and UNSW all performing well with global ranks of 21, 26 and 28 respectively.

However, others including ANU, with an employer reputation rank of 72, the University of Queensland, at 69, and the University of Western Australia, at 127, performed far worse on this measure than their overall rank.