In this paper we analyze the private final consumption expenditure in the Spanish economy from 1964 to 1994. On the basis of a simple static model [the familiar Almost Ideal Demand System -AIDS- of Deaton and Muellbauer (1980)], we use a dynamic, simultaneous and singular demand system which takes into account the disequilibrium that exists in short-run individual behaviour, supposing that only one equilibrium exists in the longrun. The resultant model offers easy of interpretation as an error correction mechanism in which the variations in the budget shares are explained by the variations of prices and total real expenditure, and also by the trend followed in reaching the long-run equilibrium between these variables.

Keywords: private expenditure. AIDS, dynamic factors, error correction.