Despite New York's heavy reliance on its vast public transit system, streets are a defining feature of the city. Manhattan's street grid plan greatly influenced the city's physical development. Several of the city's streets and avenues, like Broadway, Wall Street, Madison Avenue, and Seventh Avenue are also used as metonyms for national industries there: the theater, finance, advertising, and fashion organizations, respectively.

Answer this question, if possible (if impossible, reply "unanswerable"): What industry is Madison Avenue associated with?
advertising