Examining and Evaluating Aggregation Scale Effects on Interregional Commodity by Industry Trade Flow Estimates

This study tests the implementation of interindustry transaction flows in a national system of economic regions derived from an interregional accounting framework and initial information on interregional shipments. The interregional flows connecting states are estimated using a method based on the Commodity Flow Survey data published by the Bureau of Transportation Statistics, which adjusts the estimated interregional SAM to insure the integrity of intraregional and system-wide, national accounts. The resulting US interregional framework describes flows within and among the 51 regions We examine results of a series of trials testing the validity of the resulting interregional trade-flow data versus other data sources and estimates such as Liu and Vilain (2004). The overall difference in estimation accuracy arising from differences in the base aggregation level is a quantity that has attracted little prior attention. To address this issue this paper, in addition to estimating and comparing trade flows using aggregated sectors, also estimates the flows using the 509 disaggregated IMPLAN sectors applies aggregation only in the final comparison steps. This allows us to comment on the additional role sectoral aggregation scale may play in the relative accuracy of trade flow estimation results.