Every MBA is accredited by someone; in the terms of this website (see www.find-mba.com/accreditations ) we often assume that when we mention accreditation, we are talking about internationally-recognised accreditation, which reflects higher than average standards. As this useful article explains (www.zeit.de/2011/39/C-MBA-Akkreditierung in German) national accreditation reflects minimum levels. They are not the same thing.
If this was really the case, then why would students take degrees? Of course, it's not only the business school doesn't matter; prior work experience and language skills, plus the general labour market demand and regulations, are crucial. But if those non-school related factors were key, then outcomes would not differ for MBAs who attended different schools. In fact, they differ a lot. For example, the FT rankings are perhaps the most reliable data on salary for business school graduates. Let's compare the average salary for the four quartiles:
The quality of school clearly reflects the outcome for MBAs, and the quality of school is strongly reflected by international accreditation. Detailed data for unaccredited schools in most countries are not published, but look at these French data for the average salary levels of business schools' masters programmes: www.lepoint.fr/palmares/grandes-ecoles/grade-de-masters.php which score salaries on a scale where 1 is the maximum.
Two international accreditations: 3.1
One international accreditation: 3.7
No international accreditation: 4.8
(The levels are: 1 : > 49 000 ; 2 : 45 000-47 000; 3 : 37 000-40 000; 4 : 36 000-37 500; 5 : 34 000-36 000; 6 : 31 000 < 34 000.)
So on average each additional accreditation produced something like a 5% premium on salaries..
That's partly because the parameters for international and national accreditation are simply not the same. Anyone can see that by reading them. national accreditation is about _minimum_ standards. International accreditation is about higher than average standards. That's one reason why almost al MBAs have national accreditation, but generally it's the best that have international accreditation.
Of course there was one world-class MBA which did not have accreditation: McGill in Canada (which was accredited by EQUIS in 2013). This is a university with dual provision: they have a world-class graduate business school, with excellent resources. and an undergraduate programme which, although they are national leaders, doesn't have global standing. AACSB accredits whole institutions, not only graduate provision, and it was thought that this is the reason why they have not applied for their accreditation.
[Edited by Duncan on Apr 04, 2015]