Nationwide, expenses increased by 3.9 percent in 2015. While those necessities cost business travelers $306.91 per day on average in 2014, last year the per diem average climbed to $318.80 For specific cities, the data was different. San Francisco topped the list as the most expensive city for U.S. travelers for the third straight year with an average per diem of $547.34, up more than 7 percent from the previous year. East coast counterparts New York and Boston were close behind in the second and third spot, with daily expenses in both locations surpassing $500. Seattle and Washington, D.C. rounded out the top five. California cities snagged four spots listed in the top 10, with Santa Barbara, Los Angeles and San Jose listed in addition to San Francisco. Honolulu and Hartford, Conn. finish out the group. Hartford, at no. 10, is still above the national average with daily expenses costing $387.11. To calculate the information, Business Travel News gathered taxes and surcharges from hotels, and third-party companies collected information on rental car costs and average hotel expenses from January to November 2015, along with meal prices over a two-month time period. Specifically food costs in U.S. cities were figured by considering the gross domestic product for each location. Depending on that figure, researchers surveyed a certain number of chain and independent eateries, as well as hotel restaurants, according to a press release. Hotel costs were the sum of the sales tax, occupancy tax, surcharges and average rate across luxury, upper-upscale, upscale, midscale and economy hotels. Car rates were determined by averaging the price for various sizes -- compact, intermediate and full size -- along with taxes and fees. Get the full story at Entrepreneur and Business Travel News