Budget size variable a more global view of budgeting indicates that yhe problem is not simply one of dividing up a budget of given size but also one of determining the size of the budget itself. the government must thereby decide how resources are to be divided between private and public use. we must therefore drop the assumption of a fixed budget and reconsider project choices along with determination of total budget outlays. within the fixed budget. the opportunity cost of pursuing one public project consists of the benefit lost by not pursuing another public project. but in the open budget the oportunity cost of public projects must be redefined as the lost benefits from private projects which are forgone because resources are transferred to public use.