Recognizing that agrifood value chains (AFVCs) are essential to ensure food security and foster structural change, FAO seeks to reassess the array of policies and interventions needed to protect and strengthen AFVCs in low-income countries and fragile states. This paper aims to contribute to this initiative by shedding light on largely unaccounted-for market structures at midstream segments of AFVCs. Building on the field of Industrial Organization in economics, we develop a theoretical framework and a related simulation tool that one can inform with existing or specifically collected data. Simulation outcomes help predict how different types of shocks may affect key food security outcomes, under different levels of concentration in midstream segments of AFVCs. We illustrate this approach using data from the Ethiopian wheat AFVC in 2013.