In this study we examine changing relationships among maize prices in four global markets. In doing so, we allow the quantity of exports to play a role in both price transmission and price response. That is, we adapt threshold cointegration methods to search for critical export volumes that enhance (or diminish) the role a region’s price plays in the world market. We find that the short run response of prices in both Argentina and Ukraine is influenced by the level of Ukraine’s exports. However the period where Ukraine’s exports reached their threshold coincides with the period that Argentina imposed export restrictions on maize. We also find that there are numerous country specific price thresholds that influence each market’s short run response to a price shock.