Apart from a Keynesian adjustment, tax rates should be set so that the budget is balanced each year.  The Keynesian adjustment can be based on divergences of the unemployment rate and the GDP growth rate from long-term norms.  The maximum divergence could be on the order of ±8%.  For instance, we should currently be operating with a budgetary surplus, as we maintained in the 1990s.

I hold this belief because I judge systemic deficits likely to become burdensome for future generations, and may ultimately become untenable.