Essay on the liability rules when risks are insured
The building insurance case

Building insurance in France is governed by the amended Law of 4 January 1978 (so-called SPINETTA law) that settles a double insurance requirement against the decennial risk: DO for clients and RD for builders. This thesis introduces a theoretical framework of this system, based on models à la MOSSIN. It gives insight into a contract game between client's and builder's insurers. This game shows that a single insurer's offer is better than distinct insurers' offers thanks to its ``coordination'' value, but not to cross-subsidies. Then the study focuses on the liability rule issue which has three aspects in the building industry:
- covering builder's bankruptcy before the completion of works. This risk may justify banning the deductible in the DO contracts when a decennial damage occurs. Nevertheless, it may be efficient to endure clients a deductible when their builders go bankruptcy;
- sharing lability between builders. This issue depends upon each builder's expected loss and on the cost of liability assessment. It is sometimes efficient to resort randomly to a liability assessment. Distinct insurers' offers may dominate a single insurer's offer because the latter cannot commit. But without commitment problems, the single insurer's offer is always better than distinct insurers' offers thanks to its ``coordination'' value under symmetric information and thanks to cross-subsidies under moral hazard;
- sharing liability between clients and builders. The no-liability rule dominates the strict liability rule in an adverse selection context. This result may also be true with moral hazard when markets of rights to not decrease losses are feasible.