Optimal tax rate for top one per cent may be as high as 83%

Paper suggests cutting taxes may divert attention to wasteful bargaining

Via Daniel Elton, a new(ish) paper (pdf) by economists Thomas Piketty, Emmanuel Saez and Stefanie Stantcheva makes the case for the optimal tax rate of the richest one per cent could be as high as 83 per cent.

The authors look at three possible ways in which top incomes respond to marginal tax rates.

The first is the "supply side" channel cited by Arthur Laffer when he developed his concept of the Laffer curve. Under this channel, marginal tax rates that are too high result in people doing less work than they otherwise would. Lower tax rates thus respond to more economic activity, and greater growth and higher tax revenue. Laffer's work was used by the Reagan administration to justify cutting the top rate in the US, from 70 per cent down to 28 per cent.

The second is the "tax avoidance" channel. This is the model cited by the Chancellor when he made the decision to cut the tax rate for top earners in Britain from 50 per cent to 45 per cent. The argument is that high tax rates increase tax avoidance, but the authors argue – in common with many of the Chancellors critics – that tax avoidance can be dealt with directly, writing that:

A better policy would be to first close loopholes so as to eliminate most tax avoidance opportunities and only then increase top tax rates.

The third is the "compensation bargaining" channel. The authors argue that:

While standard economic models assume that pay reflects productivity, there are strong reasons to be sceptical, especially at the top of the income distribution where the actual economic contribution of managers working in complex organisations is particularly difficult to measure.

As a result, top workers have ample opportunity to set their own pay, through bargaining harder or influencing compensation committees. The incentives for this economically wasteful activity are higher the lower tax rates are. Just as with the supply side model, tax cuts increase the wealth of the richest in society, but unlike that model they do not also increase growth; rather, the extra money for the rich comes from those poorer than them.

The authors, using their estimates of the elasticity of the various channels (that is, the magnitude of the effect), then calculate what the optimum rates would be. Under the first model, they find it to be roughly 57 per cent – 5 per cent higher than the top British tax rate is until the cut takes effect (National Insurance for top earners is 2per cent). Assessing the second model (Osborne's preferred argument), they find that the optimal tax rate would be 62 per cent, but argue that if the correct anti-avoidance and simplification measures were put in place, it would be 71 per cent.

The third model, however, outputs an optimal rate of 83 per cent. The authors still assume a minor supply-side effect, making up 40 per cent of the total elasticity, which is why it isn't higher. That is, they still assume that high tax rates will encourage the rich to work less, but they also assume that they will encourage the rich to put more of their effort into actual work, and less of it into "compensation bargaining".

How to decide between models one and three (the authors assume that once anti-avoidance measures are put in place, model two is the same as model one)? The former predicts that lower tax leads to more work, the latter that it merely leads to higher pay. As a result, tax cuts should be correlated with higher growth. Are they? Well, no:

As a result, the bargaining model can at least be said to be as realistic as the supply-side model; and if that's the case, the optimal top tax rate for most nations is likely to be far in excess of where it is set now.

For more, see the authors in the Boston Review, VoxEU, or their original paper (pdf).

Pictured: Laffer. No, wait, laughers. Photograph: Getty Images

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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Forget the progressive alliance - it was the voters wot won it in Richmond

The Labour candidate on how voters have acted tactically for decades.

The Richmond Park by-election is both a triumph and a setback for the concept of an anti-Tory progressive alliance. As the Labour candidate, I was bombarded with emails and tweets saying I ought to stand down to prevent Zac Goldsmith being re-elected long after it was technically impossible for me to do so even if I had wanted to. I was harangued at a meeting organised by Compass, at which I found myself the lonely voice defending Labour's decision to put up a candidate.

I was slightly taken aback by the anger of some of those proposing the idea, but I did not stand for office expecting an easy ride. I told the meeting that while I liked the concept of a progressive alliance, I did not think that should mean standing down in favour of a completely unknown and inexperienced Lib Dem candidate, who had been selected without any reference to other parties. 

The Greens, relative newbies to the political scene, had less to lose than Labour, which still wants to be a national political party. Consequently, they told people to support the Lib Dems. This all passed off smoothly for a while, but when Caroline Lucas, the co-leader of the Greens came to Richmond to actively support the Lib Dems, it was more than some of her local party members could stomach. 

They wrote to the Guardian expressing support for my campaign, pointing out that I had a far better, long-established reputation as an environmentalist than the Lib Dem candidate. While clearly that ultimately did little to boost my vote, this episode highlighted one of the key problems about creating a progressive alliance. Keeping the various wings of the Labour party together, especially given the undisciplined approach of the leader who, as a backbencher, voted 428 times during the 13 years of Labour government in the 1990s and 2000s, is hard enough. Then consider trying to unite the left of the Greens with the right of the Lib Dems. That is not to include various others in this rainbow coalition such as nationalists and ultra-left groups. Herding cats seems easy by contrast.

In the end, however, the irony was that the people decided all by themselves. They left Labour in droves to vote out Goldsmith and express their opposition to Brexit. It was very noticeable in the last few days on the doorstep that the Lib Dems' relentless campaign was paying dividends. All credit to them for playing a good hand well. But it will not be easy for them to repeat this trick in other constituencies. 

The Lib Dems, therefore, did not need the progressive alliance. Labour supporters in Richmond have been voting tactically for decades. I lost count of the number of people who said to me that their instincts and values were to support Labour, but "around here it is a wasted vote". The most revealing statistic is that in the mayoral campaign, Sadiq Khan received 24 per cent of first preferences while Caroline Pidgeon, the Lib Dem candidate got just 7 per cent. If one discounts the fact that Khan was higher profile and had some personal support, this does still suggest that Labour’s real support in the area is around 20 per cent, enough to give the party second place in a good year and certainly to get some councillors elected.

There is also a complicating factor in the election process. I campaigned strongly on opposing Brexit and attacked Goldsmith over his support for welfare cuts, the bedroom tax and his outrageous mayoral campaign. By raising those issues, I helped undermine his support. If I had not stood for election, then perhaps a few voters may have kept on supporting him. One of my concerns about the idea of a progressive alliance is that it involves treating voters with disdain. The implication is that they are not clever enough to make up their mind or to understand the restrictions of the first past the post system. They are given less choice and less information, in a way that seems patronising, and smacks of the worst aspects of old-fashioned Fabianism.

Supporters of the progressive alliance will, therefore, have to overcome all these objections - in addition to practical ones such as negotiating the agreement of all the parties - before being able to implement the concept. 

Christian Wolmar is an award winning writer and broadcaster specialising in transport. He was shortlisted as a Labour mayoral candidate in the 2016 London election, and stood as Labour's candidate in the Richmond Park by-election in December 2016.