The most fundamental idea behind ZBB is that the agencies should have to justify its entire budget from the ground up each year. This is somewhat impractical, given the magnitude of the task for any national government budget, and therefore, ZBB forces each budget unit to develop contingencies for several possible levels of funding. The most basic level of appropriations is the ‘‘survival package,’’ which is the minimal level of funding needed for the organization to survive and to provide for its minimum services. Agencies might also be asked what they would do in the face of five or ten percent cuts in their budgets, and what they would require to maintain their current levels of service provision. Finally, decision packages reflecting various alternative packages of new programs are presented as the priorities of the organizations for expanding their programs. The Canadian government at one time used a system called ‘‘A, B and X’’ to get at the same range of alternatives.56 The decision packages are reviewed at successive levels in each organization to develop a set of ‘‘consolidated decision packages,’’ reflecting the priorities of the executive department along with those of its various components.