Drive less, drive better, or both? Behavioral adjustments to fuel price changes in Germany

The demand for motor fuel should decline when its price rises, but how exactly does that happen? Do people drive less, do they drive more carefully to conserve fuel, or do they do both? To answer these questions, we use data from the German Mobility Panel from 2004 to 2019, taking advantage of the fluctuations in motor fuel prices over time and across locales to see how they affect Vehicle Kilometers Traveled (VKT) and on-road fuel economy (expressed in kilometers per liter). Our reduced-form regressions show that while the VKTs driven by gasoline cars decrease when the price of gasoline rises, their fuel economy tends to get worse. It is unclear why this happens. Perhaps attempts to save on gasoline-cutting on solo driving, forgoing long trips on the highway, driving more in the city-end up compromising the fuel economy. By contrast, both the VKTs and the fuel economy of diesel cars appear to be insensitive to changes in the price of diesel. Latent class models confirm our main findings, including the fact that while fuel prices, car attributes, and household and location characteristics explain much of the variation in the VKTs, it remains difficult to capture the determinants of on-road fuel economy. Since the price elasticity of fuel consumption is the difference between the price elasticity of VKT and the price elasticity of the fuel economy, our results suggest that the fuel economy might be the "weakest link" of price-based policies that seek to address environmental externalities, such as a carbon tax.