Ok, it's a difficult one and I've used apostrophes around the terms 'middle class' and 'working class' for a reason as I'm using them as loosely as possible (their exact definitions are a bit redundant nowadays, if they ever did have any accuracy in the first place).
It's a generalisation, I know, but my experience from growing up in an area consisting of people with fairly low incomes and attending a school with children from such backgrounds, is that rap and hip hop is far more popular with the lower income demographic and that indie is more widely listened to by those who are better off and/ or more intelligent (which sounds elitist, so I aplogise).
I experienced this first hand as I picked up more on alternative rock bands when I went to college and then university. Of course there were a few exceptions - especially some very cool and intelligent chaps who listened to "proper rap" at uni, but on the whole, we educated elite tended to stick to indie bands as our bread and butter.
I hardly met that many people who listened to that many bands at school and those that did were ususally the cleverer kids who you just knew were from better families. Now I work in a school I can see that the distinction is just as stark. Most of the better behaved kids in the higher sets are emos or whatever passes for the indie bracket these days, where as those from poorer backgrounds whose prospects don't look as bright, invariably listen to rap, hip-hop, R&B (and bloody "Bounce").
It didn't used to be like this. Bands were solid prophets of the working man but that's not true today.
So what do you think? Is indie music more popular with better off and/ or more educated people and is rap/ hip-hop more popular with those from more disadvantaged backgrounds? If so, why has this happened? What is it about today's indie scene which has made it almost 'elitist' in nature?