Producer price adjustment to commodity price shocks: An application of threshold cointegration

During the 1980s and 1990s, most developing countries in Sub-Saharan Africa and Latin America implemented structural adjustment reforms, which included the liberalization of export crop markets and the abolition of marketing boards. The emergence of new marketing systems may have altered price transmission mechanisms, especially if collusion behaviors have appeared among domestic stakeholders along the marketing chain. I use threshold cointegration tools to analyze the dynamics of world price transmission to coffee growers in three deregulated markets. The methods I use allow me to test the presence of a threshold in both the cointegrating relationship and its corresponding error correction model. Over the pre-reform period, I detect asymmetric price adjustments that appear favorable to producers - deviations from the long-run equilibrium resulting from largest increases in world prices being eliminated relatively quickly - and disappear in the post-reform period. On the contrary over the post-reform period, the results suggest that largest decreases in world prices may be transmitted relatively quickly to growers. These results can be seen as expressions of a favorable pricing policy over the pre-reform period and an unfavorable influence of new private agents over the post-reform period, meaning that in some cases reforms may have failed to create competitive market structures.