Read this: New York City is additionally a center for the advertising, music, newspaper, digital media, and publishing industries and is also the largest media market in North America. Some of the city's media conglomerates and institutions include Time Warner, the Thomson Reuters Corporation, the Associated Press, Bloomberg L.P., the News Corporation, The New York Times Company, NBCUniversal, the Hearst Corporation, AOL, and Viacom. Seven of the world's top eight global advertising agency networks have their headquarters in New York. Two of the top three record labels' headquarters are in New York: Sony Music Entertainment and Warner Music Group. Universal Music Group also has offices in New York. New media enterprises are contributing an increasingly important component to the city's central role in the media sphere.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): Out of the top eight advertising agency networks in the world, how many are based in New York?
Seven