This paper proposes a diagnosis based on estimates in kilocalories of almost all plant food produced, traded and consumed in the continental Sub-Saharan Africa and Madagascar (39 countries), from 1961 to 2003. These estimates are coupled with others (inhabitants, active populations, surfaces) to first show what driving forces lead a country to raise (or not) its production of plant food calories per capita over time. These drivers, not independent from each other, are those of the equation: Production/Inhabitant = (Producers/Inhabitant) × (Hectares/Producer) × (Production/Hectare), with (Production/Hectare) × (Hectares/Producer) = Production/Producer. These tautological relationships make it possible to assess how partial agricultural productivities of land and labour evolve, and more generally to characterize some major pathways of evolution thanks to appropriate statistical and graphical techniques. These pathways appear to be varied and contrasted. The change in output per capita can then be confronted with food availabilities obtained after net imports have been added to food production, and non-food uses have been deducted (seeds, waste, etc.). This approach shows, in particular, a slight improvement in the average per capita availability across the continent. But this availability is still very low and is associated with a worsening trade balance with the rest of the world: positive at the beginning of the period, it has become increasingly negative.