|'thickness of accent' to 'stupidity level'|
In this graph we can clearly see the direct relation between someone's stupidity, and how dense their accent is. This applies to any accent from any part of the UK, and is almost universally correct when applied as an instant evaluation of someone you meet. There are some exceptions, and I'm basing this on Stephen Fry's accent being the correct usage of English, but Jamie Carragher sounds like someone is cutting a car in half with a chainsaw and viewers of the show cannot understand him.
Non-native English speakers like Pepe Reina and Lucas Leiva are well spoken enough that American viewers of the show can listen without the aid of subtitles yet Carragher might as well be a fucking Clanger for all the sense I can make of him.