PPPs cover a broad range of innovative contracting, project delivery and financing arrangements; thus, as one recent report points out, "references to public-private partnerships are wide-ranging and ambiguous, with little precision about how the term is used."5 The U.S. Department of Transportation has provided this widely adopted definition of PPPs:
A public-private partnership is a contractual agreement formed between public and private sector partners, which allows more private sector participation than is traditional. The agreements usually involve a government agency contracting with a private company to renovate, construct, operate, maintain, and/or manage a facility or system. While the public sector usually retains ownership in the facility or system, the private party will be given additional decision rights in determining how the project or task will be completed.6
A second definition-this from legislation passed in Puerto Rico in 2009-notes similar characteristics, and further emphasizes issues of mutual benefit and public interest:
A public-private partnership is an entity that couples the resources and efforts of the public sector with resources of the private sector by means of a joint investment that results in the benefit of both parties. Such partnerships are sought with the purpose of providing a service for citizens, as well as building or operating a facility or project that is held in high priority by the government… These partnerships shall be vested in high public interest, that is, the Commonwealth is neither relinquishing its responsibility of protecting such interest, nor waiving its rights to receive an efficient service, nor renouncing [the] ownership of the public assets included [in] the Partnership Contract.7
Although some authors suggest all relationships between public and private entities are partnerships,8 most definitions of PPPs include certain key characteristics, such as ultimate public sector responsibility for and ownership of an asset; sharing and allocation of risk among public and private entities; contribution of resources by both public and private partners; a contractual agreement; and transfer to the private sector of traditionally public responsibilities.9