A New Approach to CIR Short-Term Rates Modelling

It is well known that the CIR model, as introduced in 1985, is inadequate for modelling the current market environment with negative short rates, r(t). Moreover, in the CIR model, the stochastic part goes to zero with the rates, neither volatility nor long term mean change with time, or fit with skewed (fat tails) distribution of r(t), etc. To overcome the limitations of the CIR, several different approaches have been proposed to date: multi-factor models such as the Hull and White or the Chen models to the CIR by Brigo and Mercurio. Here, we explain how our extension of the CIR framework may fit well to market short interest rates