Modifying the rebound: It depends! Explaining mobility behavior on the basis of the German socio-economic panel

We address the empirical question of the extent to which higher fuel efficiency of cars affects additional travel and the way this behavioral aspect is modified by additional variables. The data set used to estimate a theoretical model of the rebound effect covers two panel waves, 1998 and 2003, taken from the German Socio-Economic Panel (SOEP). To take full advantage of the information in the data available, and to avoid problems due to possible selection effects, we estimated an unbalanced two-wave random effects panel model. Our results suggest that in line with the rebound hypothesis, car efficiency has a negative effect on the kilometers driven. That is, the lower the fuel consumption, the greater the distance driven. However, contrasting recent empirical literature about the rebound effect in the transportation sector, this seems to be true only for cars with a consumption of more than roughly 8 l per 100 km. In addition, we find a positive diesel effect, which implies that owning a diesel engine car is positively correlated with the distance driven. Both effects can be interpreted as support for the rebound hypothesis, although not in a simple linear way. Moreover, it can be shown that some “soft” variables such as certain attitudes towards the environment tend to amplify this non-linear rebound effect.