Here are some stats released by Finland:
source:
http://www.trafi.fi/palvelut/tilastot/tieliikenne/katsastus(Atleast 100 cars needs to be inspected for model to be added, therefore ForTwo and Roadster don't appear in those stats
)
Forfour (includes Brabus version also) 2013 fail % and reasons:
Year 2004 model: 16,95%; Top 1 reason: null; Top 2 reason: null; Top 3 reason: null;
Year 2005 model: 16,60%; Top 1 reason: Internal inspection system (OBD); Top 2 reason: Handbrake; Top 3 reason: Front axle;
Year 2006 model: 7,37%; Top 1 reason: Internal inspection system (OBD); Top 2 reason: Brakes; Top 3 reason: Brake light;
Forfour (includes Brabus version also) 2012 fail % and reasons:
Year 2004 model: 14,78%; Top 1 reason: null; Top 2 reason: null; Top 3 reason: null;
Year 2005 model: 15,20%; Top 1 reason: Internal inspection system (OBD); Top 2 reason: Brakes; Top 3 reason: Tires and wheels;
Year 2006 model: 9,91%; Top 1 reason: Brakes; Top 2 reason: Internal inspection system (OBD); Top 3 reason: Tires and wheels;
Forfour (includes Brabus version also) 2011 fail % and reasons:
Year 2004 model: 15,79%; Top 1 reason: null; Top 2 reason: null; Top 3 reason: null;
Year 2005 model: 13,41%; Top 1 reason: Internal inspection system (OBD); Top 2 reason: Brakes; Top 3 reason: Tires and wheels;
Year 2006 model: 5,84%; Top 1 reason: null; Top 2 reason: null; Top 3 reason: null;
Pretty interesting stats
