Tax reform TABOR style.

• Position: Trends And Transitions

WHAT: Colorado's Taxpayer Bill of Rights, a constitutional amendment approved by voters in 1992, is the toughest tax-and-spend limitation of its kind in the nation. It limits the amount of revenue the state can take in to what it was allowed the year before, plus growth plus inflation. Everything else must be refunded to taxpayers, who also must be asked to approve any tax increase.

NOT A PANACEA: Colorado's law is still considered the model for tax-cut advocates in other states. But many are considering a rainy day fund that builds up during good times and can be tapped during recessions.

WHERE ELSE?: Americans for Prosperity, a nonprofit advocacy group which...