Following the development by Sore1 in 1894 of a mathematical model for continuous, steady-state, equilibrium-stage distillation, a number of methods were proposed for solving the equations graphically or algebraically during an 18-year period from 1920 to 1938, prior to the availability of digital computers. Today, the only method from that era that remains in widespread use is the McCabe-Thiele method. What are the attributes of this method that are responsible for its continuing popularity?