The U.S. Travel projection encompasses the closure of national parks and historic sites—upon which many regional economies greatly depend—and also the cancellation of both government travel and private business travel related to government projects.
U.S. Travel's measurement of a shutdown's impact on the travel sector does not account for any potential effect on other travel-related agencies, such as Customs and Border Protection, the Transportation Security Administration, or the visa-issuing organs of the State Department.
"Though officials assured us at the time that the 2013 shutdown would not affect the work of those agencies, anecdotal evidence on that score was mixed," Dow said. "If we detect that a new shutdown is hurting those travel-related functions as well, we'll certainly stand ready to spotlight the fallout for policymakers and the public."
The 408 national park sites are spread across every U.S. state and territory in both rural and urban areas. Many regional economies are almost entirely dependent upon visitors to nearby national parks to support restaurants, lodging establishments and other businesses, and the jobs they provide.
The shuttering of national parks due to the 16-day budget stalemate of October 2013 directly reduced travel spending by $680 million, U.S. Travel calculated, or nearly $43 million per day. During that shutdown, countries such as Germany, the U.K. and China—which together account for more than eight million visitors to the U.S. annually—issued warnings to their citizens about possible shutdown-related problems and delays when traveling to and within the U.S. Even once resolved, such episodes can inflict lasting damage upon the U.S.'s brand in the competitive international travel marketplace, Dow warned.