Benjamin Franklin famously defined insanity as "doing the same thing over and over and expecting different results." As the Washington Legislature goes into session this month, Franklin's maxim comes to mind, and it's difficult to dispute its wisdom. Using the definition as a clinical guidepost, this state's approach to improving its tax system - if not quite mad - could certainly benefit from some time on the fiscal couch.

Across the political spectrum, right to left, most agree that Washington's highly regressive tax system - based as it is on one of the country's highest sales tax rates - places an unfair burden on those least able to pay. "Why would you create a tax structure that taxes poor people the most?" asks Rod Regan, who led the 1976 campaign here that removed the sales tax from food.

It's a good question. But then, Washington also consistently ranks among the bottom 10 states when it comes to funding its public schools. And, although some conservatives argue that per-pupil spending is sufficient, many who've studied the issue say increased state support would not only improve student performance, but also produce more smart people with college degrees, who in turn would put their brains to work in local industries, bolster the region's economic output, and - guess what? - generate more tax revenue with less tax burden per citizen.

And finally, when cornered (and shown accurate data presented without emotional arm-twisting), policy wonks as well as politicians of all stripes concede that lowering the sales tax, changing or even eliminating the Business & Occupation tax, and adding a modest income tax would not only make Washington's tax system fairer for everyone, but also create a more stable stream of revenue, year after year.

So there's broad consensus - and yet nothing ever changes. What gives, Dr. Freud? Why is it so difficult here to create an equitable tax system that also generates enough revenue? (Never mind what "enough" actually means; there will never be agreement on that.) And how can it be that every state, county and municipality in the richest country on Earth seems mired in perpetual tax crisis, forced to place a new initiative on the ballot every time there is a need to fill potholes or add buses?

"There's something quite odd in our state's politics when a senior and very distinguished businessperson - with great name recognition across the state - cannot pave a political consensus to make sensible changes," says Seattle University economist Paul Sommers. He refers, of course, to William H. Gates and the Washington State Tax Structure Study Committee he chaired in 2002 at the request of the Legislature. This collection of private economists, legislators and academic experts (backed by an advisory committee that included dozens of business and advocacy groups as well as a couple hundred private citizens) systematically analyzed Washington's tax structure and issued a lengthy report proposing improvements.

"They've done the research," Sommers says of the Gates committee. "Nobody has objected to the conclusions. But there is no political consensus yet to make the changes."

Mr. Gates, a formidable yet soft-spoken man, seems not quite sanguine when he says, "People are happy with the devil they know - and don't trust the devil they don't know," a metaphorical way of saying that citizens will cling to the known evil of a sales tax rather than embrace the imagined hellfire of an income tax.

In a conference room at the Bill & Melinda Gates Foundation, on East Lake Union, Gates tilts back in a plush chair as he lays out his recommendation: "A structure that includes some taxes that would provide stability to the system, and some taxes that would 'go with the flow,' so to speak," because "a system that just depends on taxes that fluctuate is not a great way to create a stable tax system." Many would agree, some grudgingly, that the most equitable and effective tax systems are constructed of three pillars: a sales tax, a property tax and an income tax. Washington has the first two; Oregon has the second two. In tough economic times, both states' revenue streams can dry up and become dangerously weak trickles. Having all three taxing sources, as Idaho does, combined with excise taxes, inheritance taxes and other, more specific revenues, is the savvy way to finance the operations of a state, Gates insists.