Abstract: A system and method for calculating, across one or more objects or portfolios, a probability distribution of values of a first parameter for one or more values of a second parameter (e.g., time). Probability distributions are assigned to each object at two or more different values of the second parameter. Each probability distribution defines a first parameter value distribution for that object at that particular value of the second parameter. Probability distributions of the first parameter across two or more objects or across a portfolio are calculated over changing values of the second parameter as a function of the probability distributions assigned to each object involved.