 The advantage of propensities over frequencies are considerable, since, on the propensity account, a probabilistic law no longer simply affirms that a certain percentage of the reference class belongs to the attribute class. What it asserts instead is that every member of the reference class possesses a certain disposition, which in the case of statistical laws is of probabilistic strength and in the case of universal laws of universal strength. On its single-case formulation, moreover, short runs and long runs are simply finite and infinite sequences of single cases, where each trial has propensities that are equal and independent from trial to trial and classic theorems of statistical inference apply.