Most growth models, including the endogenous growth ones, do not include demand. However, the evolution of demand is a necessary component of the overall growth process. In this paper we propose to take into account the influence of demand on the overall process of growth by means of our TEVECON model of economic development by the creation of new sectors. We are going to analyze the problem at three different levels: (i) no innovation could have had an impact on economic growth if nobody had purchased it. This means that consumers and or users needed to have (a) a high enough income to purchase the innovation and (b) a preference system which is compatible with the purchase of the given innovation; (ii) The relative dynamics of demand and of process efficiency have an important impact on the process of economic development. In a number of cases demand for a given good or service tends to saturate as income grows. Even when this does not happen it is still generally true that the rate of growth of consumption rises more slowly than income per capita; (iii) the role of demand is not separable from that of supply. In an innovative economy search activities affect demand, which in turn affects future search activities and thus demand in the following periods. This situation can be adequately described as the co-evolution of demand, innovation and supply.