In the Ho-Lee model, the drift of the interest rate process is presumed to be constant.

In the Ho-Lee model, when the short-term rate is above its long-run equilibrium value, the drift is presumed to be negative.

In the Cox-Ingersoll-Ross model, the basis-point volatility of the short-term rate is presumed to be proportional to the square root of the rate.

In the Cox-Ingersoll-Ross model, the volatility of the short-term rate is presumed to decline exponentially to a constant long-run level.