Crucial to sociolinguistic analysis is the concept of prestige; certain speech habits are assigned a positive or a negative value, which is then applied to the speaker. This can operate on many levels. It can be realised on the level of the individual sound/phoneme, as Labov discovered in investigating pronunciation of the post-vocalic /r/ in the North-Eastern USA, or on the macro scale of language choice, as realised in the various diglossias that exist throughout the world, where Swiss-German/High German is perhaps most well known. An important implication of sociolinguistic theory is that speakers 'choose' a variety when making a speech act, whether consciously or subconsciously.