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This article proposes an analysis of the evolution and determinants of patent filing strategies and their impact on the patent system. Its motivation resides in the evolution of practices (patent drafting and filing) over the past 20 years, characterized by a surge in the number and size of patent applications. These developments could compromise the ability of the patent system to fulfill its economic purpose of incentive to innovate, as the inflation in number and size of applications induce considerable backlogs and delays. This article presents a summary of a dissertation and different papers authored and co-authored by the same. Based on a unique database and different econometric models, these works first analyse the drivers of this evolution, notably the international diffusion of practices, the growing complexity of inventions, emerging technological sectors, and the building of large patent portfolios. The association of these developing strategies with patent value is then investigated based on traditional indicators and a new composite index of patent value. Finally, a more thorough analysis of the patent length confirms that these strategies are strongly associated with patent value, but mostly reveal that their main effect is to slow down the examination process, resulting into legal uncertainty in the patent system and raising several policy implications. Classification JEL – O31, O34, O50.