Few politicians ride into office on a more specific and rousing promise than Mark ('Tax the Rich") Dayton did in 2010. And seldom are citizens given a more detailed and credible assessment of whether a promise actually has been fulfilled than the one Minnesotans now have before them.

The assessment is the 2015 Minnesota Tax Incidence Study. It's the latest installment of a research analysis the Minnesota Department of Revenue has issued every two years for the past quarter-century.

Unique to our state, the study seeks to document exactly who pays how much in state and local taxes around here.

While it's probably not every Minnesotan's idea of a compulsive page-turner — "Fifty Shades of Gray Areas" — the incidence study is a stimulating piece of research work. It delivers pulse-pounding gratifications for fiscal conservatives and progressives alike.

A conservative's spine tingles over the study's extended discourse on the reality that businesses do not ultimately pay taxes, only people do — and that the burden of state business taxes (especially when they increase) actually falls heavily on consumers and workers.

Liberals, meanwhile, thrill to the forceful way the incidence study reveals that Minnesota taxes overall are regressive (if less so than most state tax systems), falling more heavily on the poor and middle class than on the rich.

Dayton has often invoked the Tax Incidence Study to affirm his conviction that Minnesota's tax system needs to be made more fair. In 2010, he famously ran for governor on the battle cry "Read my lips: Tax the rich" and the pledge that he would "raise taxes on the wealthiest 10 percent of the people in Minnesota … not … on the other 90 percent."

He's actually done reasonably well making good on that pledge, according to the incidence study. This proves nothing, of course, one way or the other, about whether or to what extent Dayton's policies have been good or bad for the economy.

In fact, another sobering reality the study reinforces is this: Changes in economic conditions (income levels, say) alter effective tax rates rather more than changes in state tax policy alter economic conditions.

Dayton also had to compromise on tax policy with the Legislature under both Republican and DFL control during his first term.

Anyhow, what's happened?

First, the overall effective state and local tax rate for the whole state has hardly budged. It was 11.3 percent of total household income in 2010, the year Dayton was elected. It rose to 11.5 percent in 2012, and under current law it will be 11.4 percent in 2017, according to the incidence study's projections. (This is more than a full percentage point lower than it was in the early to mid-1990s.)

As for the wealthiest 10 percent of households (2012 household incomes above $141,000), they saw their effective tax rate rise from 10.2 percent in 2010 to 10.5 percent in 2012. It will reach 10.7 percent in 2017.

The 1-percenters (incomes north of $493,000) paid 9.5 percent in 2010 and 9.8 percent in 2012. They'll pay 10.5 percent in 2017, says the study.

The regressive pattern in state taxes is visible even here, with the sincerely rich paying less than the merely rich. Also apparent is a narrowing of the gap in recent years.

And what of Dayton's pledge not to raise taxes on "the other 90 percent"? The working poor are seeing a tax cut — for example from 11.9 percent (2010) to 10.9 percent (2017) for those with incomes between $18,000 and $25,000.

The broad "middle class" — with incomes from $25,000 to $140,000 — sees no appreciable change in effective tax rates between 2010 and the 2017 projection. The rates remain between 11 and 12 percent.

So what Dayton has wrought could be summarized as follows: He's managed to leave the middle class alone while pinching the rich enough to finance a modest tax break for the poor along with hefty spending hikes for favored DFL constituencies, especially in education and local government.

Whatever else one might say about all this, it's along the lines of what Dayton promised. And given all the compromises and complications, it's no wonder it's not quite a redistribution revolution.

For example, the welcome tax cut for the working poor was achieved through boosts in refundable income tax credits and property tax refunds that had to be large enough to offset a huge cigarette tax hike Dayton claimed to accept only reluctantly.

The incidence study reminds us that the tobacco tax is far and away the most regressive of all Minnesota's levies.

But the gas tax, the study also shows, isn't much better, and that brings us to this year's legislative debate and the question of whether Dayton is declaring "mission accomplished" on tax fairness.

The gas tax hits the less-well-off much harder than it does the rich. So Dayton's determination this year to push for a large fuel tax hike to fund road construction seems a bit of a contradiction. Like the tobacco tax hike, it would make more dramatic progress toward tax progressivity more difficult.

The notion Republicans are pushing of funding transportation more in the years ahead from general fund dollars (raised in large part through the progressive income tax) rather than (regressive) gas tax dollars would seem to have some potential to serve Dayton's tax-fairness cause — even if that's not the GOP's reason for pushing the idea.

But maybe, in the end, Dayton's desire to raise more revenue and "invest in Minnesota's future" is greater than his desire to push tax fairness further.

D.J. Tice is at Doug.Tice@startribune.com.