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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Will Euroscepticism prove an unbeatable advantage in the Conservative leadership race?

Conservative members who are eager for Brexit are still searching for a heavyweight champion - and they could yet inherit the earth.

Put your money on Liam Fox? The former Defence Secretary has been given a boost by the news that ConservativeHome’s rolling survey of party members preferences for the next Conservative leader. Jeremy Wilson at BusinessInsider and James Millar at the Sunday Post have both tipped Fox for the top job.

Are they right? The expectation among Conservative MPs is that there will be several candidates from the Tory right: Dominic Raab, Priti Patel and potentially Owen Paterson could all be candidates, while Boris Johnson, in the words of one: “rides both horses – is he the candidate of the left, of the right, or both?”

MPs will whittle down the field of candidates to a top two, who will then be voted on by the membership.  (As Graham Brady, chair of the 1922 Committee, notes in his interview with my colleague George Eaton, Conservative MPs could choose to offer a wider field if they so desired, but would be unlikely to surrender more power to party activists.)

The extreme likelihood is that that contest will be between two candidates: George Osborne and not-George Osborne.  “We know that the Chancellor has a bye to the final,” one minister observes, “But once you’re in the final – well, then it’s anyone’s game.”

Could “not-George Osborne” be Liam Fox? Well, the difficulty, as one MP observes, is we don’t really know what the Conservative leadership election is about:

“We don’t even know what the questions are to which the candidates will attempt to present themselves as the answer. Usually, that question would be: who can win us the election? But now that Labour have Corbyn, that question is taken care of.”

So what’s the question that MPs will be asking? We simply don’t know – and it may be that they come to a very different conclusion to their members, just as in 2001, when Ken Clarke won among MPs – before being defeated in a landslide by Conservative activists.

Much depends not only on the outcome of the European referendum, but also on its conduct. If the contest is particularly bruising, it may be that MPs are looking for a candidate who will “heal and settle”, in the words of one. That would disadvantage Fox, who will likely be a combative presence in the European referendum, and could benefit Boris Johnson, who, as one MP put it, “rides both horses” and will be less intimately linked with the referendum and its outcome than Osborne.

But equally, it could be that Euroscepticism proves to be a less powerful card than we currently expect. Ignoring the not inconsiderable organisational hurdles that have to be cleared to beat Theresa May, Boris Johnson, and potentially any or all of the “next generation” of Sajid Javid, Nicky Morgan or Stephen Crabb, we simply don’t know what the reaction of Conservative members to the In-Out referendum will be.

Firstly, there’s a non-trivial possibility that Leave could still win, despite its difficulties at centre-forward. The incentive to “reward” an Outer will be smaller. But if Britain votes to Remain – and if that vote is seen by Conservative members as the result of “dirty tricks” by the Conservative leadership – it could be that many members, far from sticking around for another three to four years to vote in the election, simply decide to leave. The last time that Cameron went against the dearest instincts of many of his party grassroots, the result was victory for the Prime Minister – and an activist base that, as the result of defections to Ukip and cancelled membership fees, is more socially liberal and more sympathetic to Cameron than it was before. Don’t forget that, for all the worry about “entryism” in the Labour leadership, it was “exitism” – of Labour members who supported David Miliband and liked the New Labour years  - that shifted that party towards Jeremy Corbyn.

It could be that if – as Brady predicts in this week’s New Statesman – the final two is an Inner and an Outer, the Eurosceptic candidate finds that the members who might have backed them are simply no longer around.

It comes back to the biggest known unknown in the race to succeed Cameron: Conservative members. For the first time in British political history, a Prime Minister will be chosen, not by MPs with an electoral mandate of their own or by voters at a general election but by an entirelyself-selecting group: party members. And we simply don't know enough about what they feel - yet. 

Stephen Bush is editor of the Staggers, the New Statesman’s political blog. He usually writes about politics.