In the Build-Transfer-Operate (BTO) model, the private sector designs and builds a facility or piece of infrastructure for the public sector, and usually provides the financing for it. Upon completion, the title for the new facility is then transferred to the government but the private sector contractor has the contractual obligation to operate the facility and recover its investment in the project over a set number of years. These terms are usually pre-negotiated. In the U.S., the method of design-build-operate (DBO) has become a most favored alternative, especially in the water and sewage treatment industries. The U.S. practice is to have the private sector design, build and operate the facility over the long term, while the public sector provides both the construction and permanent financing using tax-exempt financing, which is more cost effective than private financing. The existence of tax-exempt financing, and its availability to creditworthy state and local governments makes the U.S. unique in the world, and skews the selection of public-private partnership when contemplating new facilities.