Per diems for 100 U.S. and 100 international business destinations. New York, Washington, D.C., Boston, San Francisco and Chicago are the most expensive U.S. cities in which to travel to conduct business, according to Business Travel News' 2009 Corporate Travel Index, its annual examination of the daily costs to stay in a hotel, eat three meals and rent a car in 100 business travel destinations in the United States. Hotel, rental car and dining costs registered only modest increases when compared with last year's index. After years of price increases, on-the-ground T&E expenses are not likely to grow much this year as the travel industry faces the slumping demand of the recession. This year, as in the past, hotels represent the single largest component of non-air expenses, which account for about 42 percent of the travel dollar, while dining expenses, which represent 30 percent of the daily cost to do business, take a larger bite out of daily travel spending than rental car pricing.