Tourism is a bigger and bigger part of NYC's economy...
Wikipedia has a lot to say about it:
Tourism in New York City is a large industry. According to NYC & Company (the official destination marketing organization for the city of New York), the top producing countries for international visitors to New York City in 2005 were the United Kingdom (1,169,000), Canada (815,000), Germany (401,000), Japan (299,000), Italy (292,000), France (268,000), Ireland (253,000), Australia (235,000), Spain (205,000), Greece (148,000), and the Netherlands (147,000).
Unlike many other destinations, New York City does not have a distinctive tourist season. With the exception of slight peaks around Thanksgiving, Christmas and New Year's, visitor arrival rates are roughly the same year-round. New York also has one of the highest hotel-occupancy rates in the country. Arrivals have remained relatively high even since the global economic crisis, due to heavy discounting and value-added pricing.
Spearheading the city's tourism efforts is NYC & Company, the city's official convention and visitor bureau currently headed by George Fertitta. It has offices in 14 countries, including Argentina, Britain, France, Germany, Ireland, Italy, Mexico, The Netherlands, Russia, Spain, Sweden, Japan, Korea and China. NYC & Company is the official source of tourism statistics for the city. The research department develops and distributes comprehensive information on NYC domestic and international visitor statistics and monitors the travel industry's impact on New York City's economy. The department also produces 14 official New York City tourism marketing publications that feature information on member hotels, museums, attractions, theaters, stores, restaurants, meeting venues, and service providers.
Double decker tour buses and boats with tour guides bring sightseers to various parts of Manhattan and other boroughs, while pedicabs and horse cabs serve those with a taste for more personal service. More adventurous tourists rent bicycles at neighborhood shops or along the Hudson River Greenway or simply walk, which is often the quickest way to get around in congested, busy commercial districts and always the best way to appreciate street life.