This paper brings time series techniques to bear on the relationships between the prices of the principal types of wheat traded internationally. In all, the relationships between eleven wheat prices (categorised by wheat quality, harvest date and port of despatch) are scrutinised to uncover the structure of the wheat market implicit in the behaviour its prices reveal. The statistical evidence supports the notion of a highly integrated market that is segmented according to wheat strength-the principal determinant of end-use. Three segments are identified: a market for 'strong' (bread-making) wheat, another for 'weak' (confectionary products-making) wheat and a third for medium strength wheat suitable for unleavened breads and noodles. Whilst informative, market integration - detected by cointegration among prices - is not altogether surprising, yet the presence of cointegration implies a causal structure, which is of more cogent interest. Among a number of complementary techniques, linkages are uncovered using an innovative concept of irreducible cointegration vectors (Davidson 1998, Barassi et al 2001) which provides new evidence on price linkages. Statistical evidence is robust and not test-dependent. Specifically, we find a dominant price leader in each sub-market. In terms of its pricing, the EU is found to play a passive role in the world market, confirming a widely held view.
