Would you civil union me?

Although the tax system is not marriage neutral in many countries, it has been found only slightly significant in determining marriage decision (Buffeteau and Echevin, 2003; Alm and Whittington, 1995). This paper tests if the tax system could alter the decision to contract a civil union, which is a less binding marital contract. In France, since 1999, couples can either contract a marriage or a civil union (pacs). I assess the impact of taxation on the decision to contract a pacs using a difference-in-differences evaluation of the 2005 reform of income taxation of newly pacsed couples. As the control group is contaminated by the reform, I propose an original estimation method based on a difference-in-differences-in-differences setting to estimate bounds to the impact of the reform. My results suggest a positive and increasing impact of taxation on pacs rates, but also a change in the timing of pacs indicating that taxation alters the decision to contract a pacs. I find a slightly significant impact of taxation on the decision to break up a pacs.