trucks are vitally important to u.s. industry, however, measuring the impact of trucking on the economy is more difficult, because trucking services are so intertwined with all sectors of the economy. according to the measurable share of the economy that trucking represents, the industry directly contributes about 5 percent to the gross domestic product annually. in addition, the industry plays a critical support role for other transportation modes and for other sectors of the economy such as the resource, manufacturing, construction, and wholesale and retail trade industries.