In November, Iowans will be voting on a proposed constitutional amendment asking whether it should be harder for the legislature to increase income taxes. The proposed amendment would create a two-thirds majority requirement for the legislature to increase the income tax.
Fortunately, Iowans do not have to speculate about what might happen if that amendment passes. Numerous states have operated under some form of supermajority requirement for decades. Arkansas adopted its requirement in 1934. Other states followed over the ensuing decades. Altogether, the states we examined provide more than 600 years of combined experience with supermajority protections in place.
That history demonstrates that these requirements do exactly what they are intended to do: They make tax increases more difficult, but they do not make them impossible.
Across the 15 states with protections most similar to what is proposed in Amendment One, lawmakers enacted 57 income tax cuts while supermajority protections were in effect. But they also enacted 11 income tax increases. Arkansas raised income taxes twice, California four times, and Delaware, Mississippi, Oklahoma, Oregon, and Washington each did so at least once.
Those increases are not something advocates of taxpayer protections should celebrate. Making it harder for government to take more of taxpayers’ income is the point of requiring broader legislative agreement. But the historical record directly challenges the argument that a supermajority requirement amounts to an absolute prohibition on future income tax increases. It does not. When lawmakers can persuade a sufficiently broad coalition of their peers that an increase is necessary, history demonstrates that the threshold can be met.
The same history provides useful context for another criticism: that restricting income tax increases will inevitably push lawmakers toward higher sales taxes. That has not been the experience of many states. Among the states we examined with protections comparable to what Iowa is considering, seven have never increased their sales tax rate while those protections were in effect. Two others increased the sales tax only once. Across the entire group, there were 24 sales tax increases and six sales tax cuts.
More fundamentally, the argument that an income tax limitation inevitably produces a sales tax increase assumes that government’s first response to a difficult budget should be finding another source of revenue. Legislatures have another option: prioritize spending and bring expenditures in line with available revenue.
The Great Recession provides a useful real-world test. California, Delaware, and Oregon had supermajority requirements applicable to income tax increases, yet all three increased income tax rates during the downturn. Nevada, which has no individual income tax but requires a supermajority for tax increases, increased its sales tax rate.
Again, the lesson is not that tax increases during emergencies are desirable. It is that supermajority requirements do not prevent legislatures from acting. They require broader agreement before lawmakers take more money from taxpayers.
As recently as 2018, Iowa placed a very heavy burden on its taxpayers. The individual rate was 8.98%, and Iowa had the highest corporate tax rate in the nation at 12%. The Tax Foundation ranked Iowa as having one of the worst state business tax climates in the nation. But Iowa has climbed nearly 30 spots in just six years as highlighted in the Tax Foundation’s 2026 State Tax Competitiveness Index which ranks Iowa 17th.
Iowa now has a 3.8% flat individual income tax, while the corporate income tax rate has fallen to 7.1% and is on a path to a flat 5.5%. Altogether, Iowa has reduced its individual income tax rate by nearly 60% and its corporate rate by nearly 41%, a reduction that will reach 54% when the 5.5% rate is fully implemented.
Amendment One would provide an additional layer of protection for those gains. A future legislature could still raise income tax rates. But instead of a bare majority being able to take more from Iowa families, farms, and businesses, lawmakers would have to build a broader consensus and make a more compelling case for doing so.
More than 600 years of combined experience in other states gives Iowans a good idea of what that means in practice. A supermajority requirement does not make tax increases impossible. It makes them harder. And when government wants to take more of taxpayers’ income, harder is precisely the point.
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