Proposition 1. If all workers are assigned to food production and none to knowledge production, then food output per capita will decrease over time. Proposition 2. A growing work force and constant ratio of workers in food and knowledge production can maintain constant per capita food output over time if there are increasing returns in the knowledge production sector. Corollary. A growing work force and constant ratio of workers in food and knowledge production can maintain constant per capita food provided knowledge per unit of food output rises over time.