آزمون تجربی از انتخاب مودال و بهره وری تخصیصی : شواهدی از حمل و نقل زغال سنگ در ایالات متحده

A generalized shipper transportation cost function is estimated to test whether coal shippers achieve allocative efficiency with respect to market prices when facing limited access to the full range of transportation services. Findings indicate that allocative efficiency with respect to market prices is achieved when shippers have access to all major transportation modes. In contrast, the condition for allocative efficiency is not met with respect to market prices when shippers’ modal choices are limited to trucking and rail services. Findings for the sample of shippers who face limited shipping choices is interpreted as suggesting an over-use of trucks relative to the use of trains due to price distortions of transportation services.

Pro-competitive policies enacted over three decades ago in the transportation industry were passed in part with the intent of creating a more efficient transportation system. Past research presents compelling evidence of non-trivial productivity gains and cost reductions in rail and trucking transportation services.2 Shippers have benefited from cost savings associated with enhanced transportation efficiency. For instance, Winston (1998) shows average shipping rates per ton-mile fell from 35% to 75% in trucking and by more than 50% for rail transportation services two decades after the implementation of pro-competitive policies. Coal shippers are a prime example of transportation services users who have benefited from enhanced efficiency and decreasing transportation operating cost. Real average coal transportation rates from 1979 to 1999 fell 29.48% and 33.33%, respectively for rail and trucking services (EIA, 2004).3 While extensive research has examined efficiency gains in the business operations of different sectors of the transportation services industry much less attention has focused on whether shippers consider market prices as an appropriate rate to use to attain an allocatively efficient mix of transportation services following the enactment of pro-competitive policies in the transportation services industry. The significance of presenting such an investigation is highlighted by noting that past research reveals that pricing behavior by carriers contributed to a misallocation of transportation services prior to the policy shift promoting inter- and intra-modal competition (Friedlaender, 1969 and Martin, 1979). This study addresses the dearth of research on shipping allocative efficiency during the current competitive business environment in the transportation industry by examining the use of different transportation modes for the delivery of coal in the US. Examining coal shippers’ choice of transportation services contributes to our understanding of the costs associated with providing an energy resource that is critical to the operations of US industries. Evidence of this commodity’s economic significance is depicted by the large proportion of coal production used to generate the electricity that powers machinery and equipment of many US industries.4 This study estimates the coal industry’s transportation cost function to test whether shippers consider market prices as viable indicators of transportation costs when making decision on the efficient combination of rail, trucking, and barge services needed to transport coal.5 Special consideration is given to the possibility that infrastructure and capacity constraints create a business environment that allows carriers to set prices that do not account for the high opportunity cost associated with relatively poor service quality.

Past research shows that prior to pro-competitive policies enacted in the late 1970s and early 1980s bulk shippers frequently misallocated transportation resources in part because rail rates did not accurately account for the full cost of transportation, especially on routes that lacked competition (Friedlaender, 1969 and Martin, 1979). This study contributes to the analysis on shippers’ use of transportation services by examining modal choices of coal shippers following the enactment of pro-competitive transportation policies. A generalized transportation cost function is estimated to examine whether coal shippers use an allocatively efficient mix of transportation services. Separate sample populations that include coal transportation information from shippers who have access to all three major transportation modes and information from shippers who have access to only rail and trucking transportation services are used to estimate cost functions. Comparing transportation findings for these two samples is significant because it allows for testing whether limited modal choices influence shippers’ ability to use an efficient mix of transportation services with respect to observed market prices. Examining transportation costs following deregulation contributes to our understanding whether enhanced competition created an environment that promotes a use of freight hauling services that is consistent with the hauling attributes of different modes of transportation. Findings on transportation modes’ elasticities of substitution suggest that rail, trucking, and barge services present competing choices for coal shippers. Hence, it is appropriate to assume that choosing among different modes of transportation is a relevant decision for coal shippers. Findings on factors of proportionality for modal shipping rates show that when access to the three major modes of coal transportation are available, coal shippers use an efficient mix of these services with respect to observed market prices. Findings on factor proportionalities for modal shipping rates show that when shippers’ access to transportation services is limited to rail and truck delivery their modal choices do not satisfy the condition of allocative efficiency with respect to observed market prices. Rather, coal shippers use an undesirable high level of trucking services relative to rail services, given rails attributes for hauling bulk freight. These results are interpreted as suggesting that transportation prices do not accurately account for the full cost of transporting coal when modal choices are limited. The undesirable mix arises because cost-minimizing shippers make decisions based on the opportunity cost of transportation not on the price charged by transportation carriers. These findings underscore the benefits derived from using the generalized transportation cost function to estimate the divergence of actual transportation prices charged to shippers and the shadow prices associated with shippers modal choice decisions.