In 2022, Germany introduced a temporary 9-euro monthly ticket for unlimited local and regional public transport. We investigate its impact on mobility patterns, including increased public transport usage, reduced car traffic, and rail network congestion. Using difference-in-difference and...

Interaction effects capture the impact of one explanatory variable x1 on the marginal effect of another explanatory variable x2. To explore interaction effects, so-called interaction terms x1x2 are typically included in estimation specifications. While in linear models the effect of a marginal...