All projections of current service budgets depend on predictions of (assumptions about) factors affecting spending and revenues such as: (1) economic growth, (2) inflation in general, (3) inflation in particular kinds of prices such as health care, and (4) numbers of people likely to be receiving government services.

Projecting revenues for long periods uses the same methods used to project revenues for short terms, such as for the next year’s budget. Projecting spending depends on forecasting workloads and prices. Put another way, it involves predicting the number of service-units to be delivered and the unit costs of delivering that service. For example, school spending projections are based on forecasting the number of students and cost per pupil.

Projected spending takes what governments now do as predictors of what they will do, assuming implicitly that all arguments for change are rejected. So no spending is shown to do things many people think should be done like paying public employees more relative to private employees, expanding park systems, reducing class sizes, or providing free community college education to all students who maintain good grades.

Nor are any savings shown to make corrections many people think should be made such as paying public employees less or reducing their pensions, cutting someone’s definition of low priority programs or waste, or getting governments out of some activities they now pursue.