MARKETS know best, said conventional wisdom on economics, until the system collapsed in 2008. Since then, there’s been a broad acceptance that growth never really “trickled down” to the middle of society, far less the bottom, and that we’d built an illusion of prosperity on a mountain of debt. Market wisdom left under-investment and inequality and precious little to go around.

However, one neoliberal nugget of nonsense remains firmly lodged in our politicians’ collective nostril. People – sensible people – still believe that cutting corporation tax makes sense. It may be ethically dubious, they argue, but it’ll boost jobs and growth. Soon, the economy will be zipping along so smoothly that the tax cut will pay for itself. This little morsel of so-called common sense is called Laffer Curve economics.

Gordon Brown did it. Alex Salmond promised it. Now, despite Theresa May’s rhetorical move away from David Cameron’s free market rhetoric, there’s a mooted plan to cut UK corporation tax to 10 per cent to screw over our stuffy continental enemies. But does cutting corporation tax improve growth and jobs? What’s the evidence?

Meet Sam Brownback, the 46th Governor of Kansas. He’s basically your classic Republican wet dream. He runs a deeply conservative state – Kansas hasn’t elected a Democratic senator since the 1930s – plus he looks like a young Ronald Reagan and he thinks abolishing abortion rights “would be a glorious day of human liberty and freedom”.

Best of all, since 2011, Brownback has launched a real live experiment in the Laffer Curve, fulfilling right-wing dreams by cutting corporation taxes for small businesses to zero. He also slashed income taxes for top earners. His policies gained glowing endorsement from – among others – Arthur Laffer, the man behind the curve and the godfather of supply side economics.

You’d think, then, that Kansas would have seen a jobs and investment miracle and that the Republicans would be hotter than ever in this good ol’ red state.

Uh uh. No siree. When Brownback faced re-election in 2014, he nearly lost to the Democrats after 100 senior Republicans endorsed their rival party’s candidate.

They were desperate: the state was near fiscal ruin. Things have continued to worsen since then. Many of Brownback’s followers are being kicked out of office.

Of course, most would expect that a government making radical tax cuts would end up with some budget problems. After all, they’ll have to cut something. So it’s little surprise to see that Kansas quickly encountered drastic under-funding in areas such as schooling.

Indeed, education got so bad, so quickly that the state’s Supreme Court said the cuts were illegal.

And health care? That’s an even more depressing story.

Yeah, but maybe that’s to be expected. Remember, the Laffer argument says that, after a few years, jobs growth will be purring along so quickly that the state will make all the money back. Soon, Kansas will have the best schools and hospitals money can buy – right?

Except Kansas isn’t purring at all. Instead, it’s coughing up an economic furball. Sam Brownback has truly been living up to his Dickensian name by turning greenbacks into excrement. Kansas has created new jobs. But the private sector has created far more jobs in the rest of the American economy, where corporation taxes remained unchanged. Similar neighbours such as Nebraska have also done considerably better. And as time goes on, and Brownback sticks to his policies, Kansas has fallen further behind in the jobs league table. During his 2014 re-election, he promised 25,000 new jobs per year. Eighteen months later, Kansas had only added 1,600.

The same goes for economic growth. Brownback’s Laffer policies have flatlined a growing economy. This matters a lot, because the Laffer case argues that the taxes will pay for themselves through better jobs growth and entrepreneurship.

For the curve to work its magic, Kansas needs to be radically outstripping the rest of America to make sure it can afford to renew all those schools and hospitals and other services they cut. Except that it’s falling behind: far behind.

Meanwhile, the state’s budget problems have left Kansas facing two credit downgrades since Brownback came to office. And the problems are only getting worse. However, although Brownback is ranked America’s least popular governor, he has his supporters. Such as Donald Trump. In a spectacular demonstration that neoliberals live somewhere along the yellow brick road of ideology, Trump has paraded his new plan for jobs: “the Kansas solution”. And the wizard himself, Brownback, looks set to join Trump’s inner circle as an adviser.

God help America.

Kansas is an extreme example, an unusually pure (and disastrous) experiment which has been allowed to continue for years without the governing party losing office.

This is thanks to the political nature of Kansas, an extreme red state.

However, nation states have generally cut corporation taxes over decades, in a “race to the bottom”. Canada, for example, has cut taxes to 15 per cent from 36 per cent in the 1980s.

A recent study by the Canadian Centre for Policy Alternatives looked at 90 years of evidence of how corporation tax rates affect growth. It concluded that tax cuts have the opposite of their intended effect. Instead of spurring investment, they encourage companies and rich people to hoard “dead money” or to chuck it into speculation. Meanwhile, cash-poor states have less ability to intervene and sort out the problems with long-term thinking.

States have been cutting the rate for decades, despite the evidence. It truly is a race to the bottom. One state walks up the yellow brick road of ideology, wanting an economic edge, so cuts the rate. Others then feel compelled to act in kind, not necessarily because it favours public welfare, but more because they don’t want to be punished by mobile companies. The overall result for everyone is public squalor. Yet, like the Soviet planners of the old days, the free-market champions insist that the experiment is only failing because it hasn’t been pure enough.

Well, Kansas is pretty damn pure, so let’s face the facts. Tax cuts don’t work. And if Brexit Britain slashes at the rate in some desperate act of economic battleships, we’ll beggar ourselves and our neighbours.

We might imagine ourselves an emerald city, but really, we’ll just be plain old Kansas: bankrupt, and lagging behind.