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QS World University Rankings by Subject: Methodology

QS World University Rankings by Subject: Methodology main image

The QS World University Rankings by Subject ranks the world’s top universities in individual subject areas, covering 42 subjects as of 2016. The rankings aim to help prospective students identify the world’s leading schools in their chosen field, with the list of subjects extended each year in response to high demand for subject-level comparisons.

Each of the subject rankings is compiled using four sources. The first two of these are QS’s global surveys of academics and employers, which are used to assess institutions’ international reputation in each subject. The second two indicators assess research impact, based on research citations per paper and h-index in the relevant subject. These are sourced from Elsevier’s Scopus database, the world’s most comprehensive research citations database.  

These four components are combined to produce the results for each of the subject rankings, with weightings adapted for each discipline.

1. Academic reputation

QS’s global survey of academics has been at the heart of the QS World University Rankings® since their inception in 2004. In 2016, the QS World University Rankings by Subject draws on responses from 76,798 academicsworldwide.

Having provided their name, contact details, job title and the institution where they are based, respondents identify the countries, regions and faculty areas they have most familiarity with, and up to two narrower subject disciplines in which they consider themselves expert. For each of the (up to five) faculty areas they identify, respondents are asked to list up to 10 domestic and 30 international institutions which they consider excellent for research in the given area. They are not able to select their own institution.

For the QS World University Rankings by Subject, the results of the survey are filtered according to the narrow area of expertise identified by respondents. While academics can select up to two narrow areas of expertise, greater emphasis is placed on respondents who have identified only one.

2. Employer reputation

The QS World University Rankings are unique in incorporating employability as a key factor in the evaluation of international universities. In 2016, the QS World University Rankings by Subject draws on 44,426 survey responses from graduate employers worldwide.

The employer reputation survey works on a similar basis to the academic one, but without the channelling for different faculty areas. Employers are asked to identify up to 10 domestic and 30 international institutions they consider excellent for the recruitment of graduates. They are also asked to identify the disciplines from which they prefer to recruit. By examining the intersection of these two questions, we can infer a measure of excellence in a given discipline.

3. Research citations per paper

For the QS World University Rankings by Subject we measure citations per paper, rather than citations per faculty member. This is due to the impracticality of reliably gathering faculty numbers broken down by discipline for each institution.

A minimum publication threshold is set for each subject to avoid potential anomalies stemming from small numbers of highly cited papers. Both the minimum publications threshold and the weighting applied to the citations indicator are adapted in order to best reflect prevalent publication and citation patterns in a given discipline. All citations data is sourced from the Scopus, spanning a five-year period.

4. H-index

Since 2013, a score based on ‘h-index’ has also been incorporated in the QS World University Rankings by Subject. The h-index is a way of measuring both the productivity and impact of the published work of a scientist or scholar. The index is based on the set of the scientist’s most cited papers and the number of citations that s/he has received in other publications.

The h-index can also be applied to the productivity and impact of a group of scientists, such as a department or university or country, as well as a scholarly journal. The index was suggested by Jorge E. Hirsch, a physicist at UCSD, as a tool for determining theoretical physicists’ relative quality, and is sometimes called the Hirsch index or Hirsch number.

How are large research collaborations assessed?

For 2016, QS has introduced an improvement to the assessment of research papers with authors from an exceptionally large number of institutions. This situation occurs most frequently in scientific subjects such as high-energy physics, cosmology or genomics, where large-scale international collaborations are common.

If each institution involved in such papers receives full credit for the citations, even very important papers can end up accounting for too large an impact on the ranking results. Yet it is equally undesirable to give each institution a share of the credit, as this could discourage research collaborations among groups of any size.

With the support of the QS Global Academic Advisory Board, the solution adopted is to omit any paper with more than 99.9% of the average number of institutional affiliations for the subject in question. This replaces the previous approach of omitting all papers with more than 10 institutional affiliations, which unfairly penalised certain scientific fields, such as medicine.

Weightings

As research cultures and publication rates vary significantly across academic areas, the QS World University Rankings by Subject applies a different weighting of the above indicators in each subject. For example, in medicine, where publication rates are very high, research citations and the h-index account for 25% of each university’s total score. On the other hand, in much lower publication areas such as history, these research-related indicators only account for 15% of the total ranking score. Meanwhile in subjects such as art and design, where there are too few papers published to be statistically significant, the ranking is based solely on the employer and academic surveys.

Further details can be found on the QS Intelligence Unit website. 

This article was originally published in February 2014. It was last updated in March 2016.

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Written by QS Staff Writer

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13 Comments
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The new normalization of citations per faculty is quite flawed. Primarily Science institutions are getting their citation per faculty numbers reduced, favoring institutions who do not publish as much. A subjective bias no longer ranks citations per faculty, but instead favors some randomly created weighting of citations per faculty. Citation heavy Imperial College London ranks over 100 in citation per faculty, and drops from number 2 ->8. As it is a science institution there is no amount of reasonable citations it could perform to raise in rankings.

Hi, I would like to know, the date of the data for the last ranking. Dec 2015? Jan 2016? thanks.

Hi,
I would like to have a better understanding of the Employer Reputation survey, and am curious if you can provide any details about the employers that are surveyed. For example while I can see that there are approximately 44k responses, how many organisations does this represent? What is the geographic spread of the responses? What are the roles of the responders; recruiters from HR, CEO, something else? It would be really helpful if a list of the companies responding to the survey could be made available. Any further insight would be appreciated. Thanks.

Hi Richard, a full breakdown of the employer survey respondents by geography and sector is available here, and more information on the Employer Reputation indicator can be found here. 

I would like to know a little more about how institutions qualify for inclusion in a subject ranking. With regards to the academic and employer reputation indicators, what is the minimum score that is required? Also, what is the required number of papers that must be published in the previous 5 years?
Many thanks,
Petrina

Hi Petrina, you can find out more about how universities qualify for the subject rankings and what minimum scores are required for the academic and employer reputation indicators here. (Scroll down to the bottom to see tabs with information on each of the indicators). Hope this helps! 

I had a similar question to Paul. What is the exact citation window you use; which period is included here? And do the papers come from exactly the same period, or is the publication window different from the citation window? Thank you for your answer.

Hi Cathelijn. For the citations, we use a five-year window to take the data from the Scopus database. This is the same window used for the h-index as well. Hope this helps to clarify.

Hi Laura,

Thanks for the answer! However, I don't quite get what you mean. Do you take both the publications from a five-year window (say, 2010-2014 for the 2015 ranking) and count the citations to these publications within the same period (so also 2010-2014)? Or do you use another approach, for example a sliding citation window? Thanks a lot.

Hi there,

I would like to echo Paul's question. Could you elaborate some more on the citation counting. What is the exact window for citations, e.g., 2010-2014 for the 2015 ranking? And what is the window for publications? Do they need to have been published in the same five-year period? Thank you!

I am leaving in a very poor Africa nation ( Ethiopia) so i need the help of very rich European country to upgrade my degree to Master so how can i get the opportunity to learn abroad ?

Hi Epheram, if you'd like to study in Europe, you can find scholarships for the region here. You might also like to read our guide to funding your graduate studies. Hope this helps! 

Would it be possible to know a little more about the 'Citations per paper' measure? Specifically, it would be helpful to know (a) the time period over which this is measured (b) whether it is limited to citations relating to outputs published within this time period or if it is measuring the number of citations over the time period regardless of the actual date of publication? Many thanks

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