Summaries This article combines the GCC and Convention Theory frameworks to compare the value chains for agro?commodities before and after the decade 1980–90. Crudely, this period was a watershed between producer?driven and buyer?driven forms of organisation. Subsequently, two types of buyer?driven chain have become differentiated: one with low entry barriers that is experiencing downgrading, and one with high entry barriers that is experiencing upgrading. A major policy challenge is to find institutional means of lowering the entry barriers to the second kind of chain, while preserving the upgrading trajectory. This article applies value?chain analysis to an agricultural ‘commodity’ which is in the process of significant change in final product markets. By focusing on the capacity of value?chain analysis to map input?output relations, and by identifying power asymmetries along the chain, it is possible to analyse the factors explaining inter?country distributional outcomes in this sector. A major conclusion is that we are witnessing a simultaneous process of power concentration in importing countries and power deconcentration in producing countries. It is hypothesised that similar trends can be observed in other agricultural?based value chains.