Critics of pro-growth tax policy are perpetually vigilant for opportunities to condemn the Laffer Curve as a free-lunch scheme pushed by political hacks who want to claim that all tax cuts pay for themselves. And while it is true that some tax-cut advocates are too aggressive in their assertions, the critics often are guilty of knocking down straw men (while dodging the real issue, which is whether the right kind of tax rate reductions lead to growth and the degree to which that higher growth leads to revenue feedback).

The latest skirmish in this long-running battle revolves around a Wall Street Journal editorial on corporate tax rates. The WSJ’s editorial included a graph showing corporate tax rates and corporate tax revenue and included a line purporting to show that the revenue-maximizing corporate tax rate is somewhere between 25 percent and 30 percent, a bit of artwork that has been criticized by Brad DeLong and Mark Thoma.

But if the Laffer Curve is an absurd notion, why did the World Bank (hardly a bastion of supply-side thinking) report that “high tax rates do not always lead to high tax revenues. Between 1982 and 1999 the average corporate income tax rate worldwide fell from 46% to 33%, while corporate income tax collection rose from 2.1% to 2.4% of national income. … A better way to meet revenue targets is to encourage tax compliance by keeping rates moderate.” And if the Laffer Curve is discredited, someone needs to tell the European Commission (a bureaucracy infamous for trying to harmonize corporate rates at high levels), which recently admitted that “it is quite striking that the decline in the corporate income tax rates has not resulted, so far, in marked reductions in tax revenue, both the euro area and the EU-25 average actually increasing slightly from the 1995 level.”

Or, shifting from corporate taxes to broader measures, how about new research from two German economists (neither of whom are known as supply-siders), which reported that, “We find that for the US model of a labor tax cut and of a capital tax cut are self-financing in the steady state. In the EU-15 economy of a labor tax cut and 85% of a capital tax cut are self-financing.”

Or what about the experience of Ireland? Would critics deny that that there has been a Laffer Curve effect in Ireland, where corporate tax revenues have jumped from less than 2 percent of GDP to more than 3 percent of GDP (a result that is all the more impressive considering the rapid growth of GDP in the Emerald Isle)? And are they really willing to categorically deny any supply-side response following the Reagan tax rate reductions? The 1997 capital gains tax cut? The 2003 tax rate reductions?

Tax-cut advocates should be careful not to over-state the revenue feedback caused by tax cuts -- especially for tax cuts that are poorly designed (such as the Keynesian rebates and credits adopted in 2001). But opponents of lower tax rates are equally misguided (or disingenuous) if they blindly assert that changes in tax policy never impact economic performance, and thus never cause revenues to rise or fall compared to static estimates.

Unfortunately, revenue estimating today is based on the absurd notion that tax policy does not affect macroeconomic performance. During 12 years of GOP rule in Congress, Republicans failed to modernize the revenue-estimating process at the Joint Committee on Taxation. No wonder they deserved to lose.