How coupled economic activity and freight transport demand really is: concept of a new economic indicator

Economic activities imply freight transportation. The relationship between GDP and ton kilometres or transport intensity, however, is disputed. But does this change when taking a detailed economic indicator into account? In this paper, the relationship between the amount of transported goods and economic activities by industries is investigated. Using EUROSTAT supply-use tables for Germany, we developed a new economic indicator with which the interdependency between 59 industries (NACE classified) their 59 products (CPA classified) and the transport demand distinguished into 24 types of goods (NST/R classified) can be shown. The novelty on this indicator is the inclusion of information taken from supply-use tables. The approach assumes that the driving industries for the supply and use of products are also the main drivers behind the transportation of these products and that their gross value added correlates with the amount of goods transported. Depending on the products, either the supply side might be the major driver for transportation or the use side. Therefore, both options are tested by a regression analysis. In the results, we can firstly observe a strong interdependency between the majority of the transported goods and the developed economic indicator. This enables us to statistically explain 16 of 24 commodities which represent 91% of the amount of the transported goods in Germany. Secondly, we also correlated the ton kilometres to the economic indicator and found a strong correlation for 17 of 24 resp. 88% of the goods. We finally are able to provide three statements on the question “How coupled transport demand and the economy really are”: 1. The information from supply and use tables and the introduced economic indicator are useful to investigate the coupling/decoupling between economy and transport in a new way. 2. A strong coupling between economy and transport, measured in tonnes transported or ton kilometres can be found using the “right” indicators. 3. The correlations indicate that the demand side of the economy drives the transport demand (i.e. a use table based indicator shows better correlation)