At a seminar recently at Ural Federal University in Ekaterinburg the question was raised whether we could evaluate and rank rankings.
That's a tough one. Different rankings have different approaches, audiences and methodologies. The Shanghai rankings embody the concerns of the Chinese ruling class, convinced that salvation lies in science and technology and disdainful -- not entirely without reason -- of the social sciences and humanities. The Times Higher Education world rankings have claimed to be looking for quality, recently tempered by a somewhat unconvincing concern for inclusiveness.
But it is possible that there are some simple metrics that could be used to compare global rankings. here are some suggestions.
Universities are big places typically with thousands of students and hundreds of staff. In the absence of administrative reorganisation or methodological changes we should not expect dramatic change from one year to another. Apparently a change of four places over a year is normal for the US News America's Best Colleges so nobody should get excited about going up or down a couple of places.
It would seem reasonable then that rankings could be ordered according to the average change in position over a year. I have already done some calculations with previous years' rankings (see posts 09/07/14, 17/07/14, 04/11/14).
So we could rank these international rankings according to the mean number of position changes in the top 100 between 2013 and 2014. The fewer the more stable the rankings.
1. Quacquarelli Symonds World University Rankings 3.94
2. Times Higher Education World University Rankings 4.34
3. Shanghai ARWU 4.92
4. National Taiwan University Rankings 7.30
5. CWUR (Jeddah) 10.59
6. Webometrics 12.08
Consistency and Redundancy
It is reasonable that if the various ranking indicators are measuring quality or highly valued attributes there should be at least a modest correlation between them. Good students will attract good teachers who might also have the attributes, such as an interest in their field or reading comprehension skills, required to do research. Talented researchers will be drawn to places that are generously funded or highly reputed.
On the other hand, if there is a very high correlation between two indicators, perhaps above .850, then this probably means that they are measuring the same thing. One of them could be discarded.
Some rankings have adopted the practice of putting universities into bands rather than giving them individual scores. This is, I suppose, a sensible way of discouraging people from getting excited about insignificant fluctuation but it might also suggest a lack of confidence in the rankers' data or the intention of selling the data in some way, perhaps in the guise of benchmarking. Since 2010 THE have bundled indicator scores into clusters making it very difficult to figure out exactly what is causing universities to rise or fall. Rankings could be ranked according to the number of universities for which overall scores and indicator scores are provided.
It would be very easy to rank rankings according to the number of universities that they include. This is something where they vary considerably. The Shanghai ARWU ranks 500 universities while Webometrics ranks close to 24,000.
Some rankings such as ARWU, the NTU rankings (Taiwan), URAP (Middle East Technical University) measure only research output and impact. The THE and QS rankings attempt to include metrics related, perhaps distantly, to teaching quality and innovation. QS has an indicator that purports
Some rankings award a disproportionate weighting to a single indicator, QS's academic survey (40%), THE's citation indicator (30%). Also, if a university or universities are getting disproportionately high scores for a specific indicator this might mean that the rankings are being manipulated or are seriously flawed in some way.
How do we know that rankings measure what they are supposed to measure? It might be possible to measure the correlation between international rankings and national rankings which often include more data and embody local knowledge about the merits of universities.
How long would it take to check whether the rankings have given your university the correct indicator score? Try it for yourself with the Shanghai highly cited researchers indicator. Go here and find the number of highly cited researchers with Harvard as their primary affiliation and the number with your university. Find the square root of both numbers. Then give Harvard a score of 100 and adjust your university's score accordingly.
Now for the THE citations impact indicator. This is normalised by field and by year of citation so that the what matters is not the number of citations that a publication gets but the number of publications compared to the world average in 334 fields and in the first, second, third, fourth, fifth or sixth year of publication.
Dead simple isn't it?
And don't forget the regional modification.
I hope the next post will be a ranking of rankings according to stability.