*Since 2000, a series of national plans have been implemented in France to increase collective childcare provision. On the period 2000-2016, 150000 subsidized childcare places have been created with disparities in the timing and magnitude of the expansion across municipalities. Using French administrative data and detailed information on the number of childcare places by municipality, I plan to exploit these disparities to study the impact of collective childcare expansion on fertility, marriage stability and parental leave uptake.

**Inequality and environmental degradation are hot topics in the public debate. Pollution taxes can be seen a useful tool to make agents internalize environmental externalities and address the pollution issue, but they are often criticized as agents are heterogeneously affected by them. Implementing such taxes can create political opposition, such as in Canada in 2021 or the French Yellow vests movement in 2018. In this paper, I plan to analyze whether it is possible to implement a carbon tax using already existing taxes in order to obtain the first-best and second-best outcomes. Building a dynamic Ramsey model with a climate externality and heterogeneous households, I intend to study the effect of using existing taxes instead of a carbon tax on inequality, pollution and dynamic properties of the model. I also plan to run a quantitative analysis to check whether the new tax rates fall into existing tax ranges.