While PPPs have the potential to achieve these efficiency gains, the public has not yet fully realized the benefits. One reason is that PPPs have sometimes been used to anticipate future revenues and thereby temporarily improve budgets-rather than used to achieve efficiency gains. A second reason some PPPs have been less successful than they could have been is that PPP contracts are incorrectly designed, by misallocating risks, or by being excessively inflexible, or, at times, excessively flexible. Examples of each type of problem are discussed below: