how profitable is hip-hop culture within america, in terms of revenue per year?

You asked about profitability of Hip Hop culture and then asked about revenue.

1. How do you define the 'market'?
Do you include the sale of 'urban clothing'?
Ad revenue on hip hop radio stations?
Drinks sold at night clubs?

Here is some of the things you should look at

a) Music sales including online downloads
b) Clothing sales for 'urban' brands
c) Expenditure patterns from the youth market (15-25) 

My personal guess is over US$ 200 Billion globally


http://www.the-infoshop.com/study/pf16755_african_american_us_toc.html

The price is US$ 3500 for a copy