I'm disappointed to see Tim Worstall falling for an old canard. He points out that the share of income tax paid by the top 1% has risen hugely since 1979-80 and infers: "Looks like lowering rates can indeed increase tax collected."

Post hoc ergo propter hoc, dear boy.

It's quite possible that the share of tax paid by the top 1% rose since the 1980s not because of Laffer curve-type incentive effects, but because some other processes have increased the share of incomes going to the richest 1%.

One of these was that high-paid jobs expanded because the financial sector grew faster the the rest of the economy: since 1990*, business services and finance has grown by 129% in real terms whilst overall GDP has risen 61%.

Another is that "superstar (pdf) effects" have increased in importance, such that top bosses, entertainers, lawyers and sportsmen can earn more now than they did in the 80s.

These processes might have been independent of the cut in top taxes by Nigella's dad in 1988. I say this because the share of incomes going to the top 1% seems to have grown faster between the mid-90s and mid-00s than it did in the few years immediately after Lawson's cut. Sure, incentive effects might work with a long lag - but the data are also consistent with the tax cut being independent of the things generating rising top incomes.

What's more, if higher top taxes did have incentive effects, they might have incentivized not genuine wealth creation, but rather rent-seeking activities which increased the share of the top 1% at the expense of others. Such activities include corporate downsizing, offshoring, lobbying and the introduction of power-biased technologies.

There's one big piece of evidence to suggest that what's happened since the mid-80s is an increased share for the top 1% rather than genuine wealth creation. It's that aggregate economic performance hasn't improved since the Lawson tax cut. I pointed out the other day that trend growth in GDP per capita hasn't changed since then. And I'd add that labour productivity has actually fallen. Since 1988Q2, GDP per hour has rise by 1.8% per year, compared to 2.5% per year between 1971 (when ONS data began) and 1988Q2.

Of course, you might argue that economic performance would have been worse, in the absence of the cut in top taxes. But it would be unwise for rightists to do so; it would imply that other Thatcher reforms either depressed growth or failed to improve it.

I say all this not to argue against top tax cuts, but merely to point out that you need much better evidence than a rise in the share of tax paid by the top 1% to justify them.

* Chosen because that's when ONS data begins.