Economic and structural determinants of the demand for public transport: an analysis on a panel of French urban areas using shrinkage estimators
This paper presents a panel data analysis of annual time series from 1975 to 1995 for 62 urban areas in France. It compares the results obtained from a conventional fixed-effects (FE) model with a Bayesian approach (shrinkage estimators), which allows the computation of elasticities for each urban area. First, considering only three economic determinants (vehicle km, income and price), we show the sensitivity of the estimates to the time period used for the estimation. On the basis of these models, public transport appears as an “inferior good” (i.e. its income elasticity is negative). By combining economic determinants with structural determinants (i.e. population ageing, urban sprawl and growing car ownership) synthesized in a single indicator, we show that this ‘income effect’ is in fact mainly a “motorization effect”. The competition with the automobile also appears through the cross-elasticity to the fuel price. Finally, the impact of supply is decomposed into a dominant effect of quantity (seats kilometres), and the weaker effects of quality (frequency and density of network). The major conclusion is that the downward trend in public transport patronage is mainly due to increasing car ownership, and that this effect will be less and less important over time since the growth of the car stock is decelerating. In addition, the use of public transport is quite sensitive to the volume supplied and to its price, which makes the financial equilibrium of this industry problematic.