Assumptions about taxable income elasticity

On 21 March, the Chancellor of the Exchequer, George Osborne, delivered the 2012 Budget for the UK. The details of the tax and benefit changes can be found in the Budget Report, with the Treasury’s summary of the tax changes here.

One of the key elements in the Budget was the reduction in the top rate of income tax from 50% to 45% from April 2013. The Chancellor argued that the introduction of the 50% rate in 2010 had raised very little extra tax revenue. Partly this was the result of people managing their tax affairs so that they could bring forward income to the year before the 50% rate was introduced – a practice known as forestalling. People are likely to do the reverse with the latest tax change and delay receiving income until next year. For details of the effects of forestalling, see the Office for Budget Responsibility’s Economic and fiscal outlook charts and tables Box 4.2a.

But part of the reason for the 50% tax rate raising relatively little has been the effect on incentives. A rise in the top rate of income tax can encourage people to move from the country – or move their incomes; it may discourage top earners from working more; it may encourage people to engage in various tax avoidance schemes; it may encourage people to evade taxes by not declaring all their income.

The effect of a rise (or fall) in the marginal income tax rate (t) on taxable income is given by the taxable income elasticity (TIE). This is defined as the proportionate change in taxable income (Y) divided by the proportionate change in the net-of-income-tax rate (r) (where r = 100 – t: i.e. the percentage of an extra pound that is not paid in income tax, but is retained by the taxpayer for spending or saving). TEI is thus ΔY/Y ÷ Δr/r. The larger the disincentive effect of raising taxes, the more will taxable income fall and hence the higher will be the value of TIE.

The Office for Budget Responsibility (OBR) in 2010 based its calculations on a TIE of 0.35 for the rise in the top marginal rate of income tax from 40% to 50%. This means that for each 1% fall in the net-of-income-tax rate, taxable income would fall by 0.35%. With a TIE of 0.35, the OBR calculated that the new top rate would bring an extra £2.9bn per year by 2011-12 (after allowing for any temporary residual effects of forestalling). However, the OBR now believes that the TIE is significantly higher and that the 50% rate will bring only an extra £0.7bn in 2011/12.

In its analysis of the effects of a cut in the top rate from 50% to 45%, the OBR has assumed a TIE of 0.45.

Turning to the costing of the move to 45 per cent, measured against our baseline that reflects the new information on the 50 per cent yield, we have endorsed as reasonable and central the Government’s estimate that the underlying cost would be around £0.1 billion in 2013-14, based on an assumed TIE of 0.45. The figure is as low as this because a TIE of 0.45 implies that the revenue-maximising additional tax rate is around 48 per cent. Moving from just above to just below this rate would therefore have very little revenue impact. Moving the additional rate back to 40 per cent would take it further below the revenue maximising rate and would thus be more expensive at roughly an additional £600 million. But for the reasons set out above we would again emphasise the huge uncertainties here.

The government’s arguments for reducing the top tax rate, therefore, are that it will have little effect on tax revenue, but would have a significant effect in encouraging inward investment, discouraging emigration of high earners and encouraging high earners to work more.

Articles
Rich tax cuts offset by changes to relief Financial Times, Vanessa Houlder (21/3/12)
Budget 2012: A big debate about small numbers (cont’d) BBC News, Stephanie Flanders (21/3/12)
Budget 2012: End of 50p tax, but 45p rate here to stay The Telegraph, Robert Winnett (21/3/12)
Budget 2012: Top income tax rate ‘won’t go any lower than 45p’ This is Money, Tim Shipman (22/3/12)
Why is tax avoidance a reason for letting people off tax? New Statesman, Alex Hern (22/3/12)
Study: Millionaires Don’t Flee States Due To Tax Hikes Think Progress, Pat Garofalo (22/3/12)
Laffer Curve Fun, with a side serving of nepotism Mark Wadsworth blog (22/3/12)
Budget 2012: are we really all in this together? Guardian, Polly Curtis (21/3/12)
Did the 50p tax rate really raise less than £1 billion in 2010/11? Touch Stone, Howard Reed (22/3/12)
45p: Power beats evidence Stumbling and Mumbling, Chris Dillow (22/3/12)

Reports, documents and presentations
Economic and fiscal outlook – March 2012 OBR
Budget 2012 HM Treasury (21/3/12)
Budget 2012 IFS (March 2012)
The Exchequer effect of the 50 per cent additional rate of income tax HMRC (March 2012)
Can More Revenue be Raised by Increasing Income Tax Rates for the Very Rich? IFS, Mike Brewer and James Browne (2009)
The 50p income tax rate IFS, James Browne (March 2012)

Questions