Spatial Price Linkages of Brown Cowpea ( Vigna unguiculata ) in Nigerian National Markets

The study was undertaken to examine the existence and the level of market integration among selected cowpea markets in Nigeria. Co-integration and Granger causality tests were used to measure market integration and leading markets between producing and consuming regions. Result of the co-integration test using Johansen likelihood procedure to determine the number of co-integrating relations indicates that the wholesale prices of brown cowpea in the selected markets in Nigeria are co-integrated. The pairwise Granger causality test shows that Umuahia–Monday, Umuahia–Giwa, Giwa–Bodija and Bodija–Giwa market pairs rejected the null hypothesis of no causaality. Moreover, there is a bidirectional Granger causality between Giwa and Bodija markets at 5 per cent significant level. Thus, Giwa and Bodija are the markets occupying the dominant position in the Nigerian brown cowpea price formation and transmission. Few of the markets are spatially linked by trade, so there is low market integration between the regional brown cowpea markets in Nigeria.