Dual Model

While the dual (CCR model) yields the same efficiency score as the primal model, it provides another way at looking at the same problem. Mathematically the dual may look more complex, but is much faster to solve as it has only as many constraints as there are factors. To  see if a unit is efficient or not, the dual model internally tries to construct a hypothetical composite unit out of existing units that will outperform the given unit. If it can, the unit in question is inefficient, otherwise it is efficient.