A system for generating a model of unknown values of several rate series at specified times includes a computing device configured to receive input indicative of the parametric model type of the unconditional rate dynamics; receive input indicative of a known or unknown rate value for each rate series and for each specified time into the computing device; generate the values of the known rate changes; generate an unconditional multidimensional probability distribution of the known and unknown rate changes; generate a multidimensional probability distribution of the unknown rate changes conditional on the known rate changes taking their known values; and provide output from the computing device indicative of the modelled values of the unknown values of the several rate series. The several rate series have unconditional rate dynamics characterized by a parametric model type in several dimensions, each rate series having at least one known value.