Similar Amendments in Practice
Fifteen U.S. states have some form of constitutional or statutory supermajority requirement for tax increases. Below are examples of how similar bills have impacted their states.
Missouri's Hancock Amendment
Missouri passed the Hancock Amendment in 1980, requiring tax increases above a specified threshold to be approved by voters, not legislative supermajority. Assessments of Hancock's effect differ. Supporters credit it with restraining state revenue growth. Critics point to its erosion through court rulings and legislative workarounds, the state's ongoing reliance on fees and local property taxes to fund services, and pressures on Missouri's public education and infrastructure funding.
Colorado's TABOR
Colorado's Taxpayer Bill of Rights (TABOR) is the most-studied US example of a state-level constitutional restriction on taxation. Non-partisan research generally finds TABOR has succeeded at restraining state revenue growth while contributing to Colorado's decline in national rankings for K-12 per-pupil spending, higher education funding, and infrastructure investment relative to peer states.
Broader Cross-State Evidence
The Center on Budget and Policy Priorities analyzed tax revenue data from 41 states over three decades (1980–2009) and found that states with strict supermajority requirements levy taxes at nearly identical levels as other states, on average. In both groups, state and local taxes remained flat as a share of personal income over the period studied. This finding suggests that supermajority requirements have not measurably lowered long-term tax burdens compared to peer states without them, though they may affect the pace and timing of tax changes.