Aging is an important challenge for pension schemes, especially for social security plans mainly ô°‚nanced by PAYG (Pay as you go) and based on a DB formula (Deô°‚ned Beneô°‚t). In particular, demographic risks induce important increases of the contributions and threaten the ô°‚nancial sustainability of such schemes. On the other hand, switching to Deô°‚ned Contribution plans can be a solution in terms of funding but introduce signiô°‚cant risks in terms of social adequacy. The purpose of this paper is to study hybrid solutions between DB and DC in a stochastic environment. In particular, we simulate for various risk sharing strategies, the evolution of contributions and beneô°‚ts by introducing risk factors inô°ƒuencing the demographic dependence ratio (fertility, longevity, baby boom). We study the mean evolution of these processes as well as their value at risk.