Transporte

Transportation 30: 245–260, 2003  2003 Kluwer Academic Publishers. Printed in the Netherlands.

On the goods-activities technical relations in the time allocation theory
SERGIO R. JARA-DÍAZ
Universidad de Chile, Casilla 228-3, Santiago, Chile (E-mail: jaradiaz@cec.uchile.cl)

Key words: consumer theory, time allocation, travel behaviour, value of time Abstract. In areas like householdproduction and travel choice, time assigned to the different activities plays a key role in addition to consumption as the main variables in utility within the consumer behaviour framework. However, a comprehensive conceptual structure to understand the technological relations between goods consumption and the assignment of time to activities is still lacking. In this paper the problem is reviewed andall possible relations between goods and time are re-formulated. Two general functions are defined and proposed to account for all these relations, forming a new taxonomy for the technical constraints. The resulting consumer behaviour model is used to obtain general expressions for both the value of saving time in constrained activities like travel, and the value of leisure.

1. IntroductionTime allocation theory has received contributions from many perspectives. Home production (household work), labour supply and travel choice are probably the most fruitful from the viewpoint of understanding both consumer behaviour and the individual valuation of time. On the other hand, at this stage of human evolution the “lack of time” complaint is part of daily life in most developed anddeveloping countries, with all its legacy of anguish and stress that makes Woody Allen’s films so attractive and psychiatrists so rich. Although expectancy of life at birth increases constantly and we have access to gadgets that permit a more efficient use of time like never before, social, professional and personal commitments seem to swallow this potential freedom in a never-ending and paradoxicalprocess of mutual reinforcement. Nevertheless, time is still only a guest in consumer behaviour theory. A first glimpse at the relevance of time in consumer theory can be obtained using the money budget constraint for one individual: ceteris paribus, more work usually means more money. As a consequence, however, a time constraint becomes mandatory because one cannot work continuously (although somewould claim they could). But not only resting is necessary and appreciated, which is why leisure was eventually introduced in the utility function

246 for the labour supply theory; the fact is that consumption requires time as well and activities require goods. It is this crucial though neglected point that we want to address here, namely the relations between goods consumption and timeassignment to activities and its impact on the value of saving time in activities like travel. Identifying clearly these relations seems like a necessary step to keep on building modelling capabilities to improve our understanding of consumer behaviour. The evolution of time allocation theory within the consumer behaviour framework can be looked at from many angles. One is, of course, the variablesconsidered in utility. The traditional approach included goods only, but it evolved to include goods and consumption time as inputs for “final goods” (Becker 1965), and then goods and activities as direct sources of satisfaction (DeSerpa 1971). A revolutionary step (not sufficiently recognised) was taken by Evans (1972), who postulated time assigned to activities as the only argument in utility. In lateryears we have witnessed variations on these, depending on what is the authors’ emphasis (for instance, the dynamic formulation of Winston 1987). A second (complementary) perspective is that of the type of constraints considered. In addition to the traditional income budget constraint, a time availability constraint was first included (Becker 1965; Johnson 1966; Oort 1969). Soon after, it was...