NOTES: Percentages may not add to 100 because of rounding.Other
transportation and support activities cover
scenic and sightseeing transportation, support activities for transportation
(e.g., private air traffic control services, marine cargo handling, and motor
vehicle towing), and couriers and messengers.
SOURCE: U.S. Department of
Transportation, Research and Innovative Technology Administration, Bureau of
Transportation Statistics, calculations using data in table 9-5b.