Research

Taxation and Migration by the Super-rich (updated!)
with Arun Advani & Andy Summers, Working Paper, 2025.

We study international migration responses of the super-rich to taxes using UK administrative data and a difference-in-differences design. We exploit a reform that removes access to a tax break on foreign income for foreigners based on their number of years in the UK, allowing us to compare individuals with similar incomes and wealth. The reform reduces the net-of-tax rate of affected taxpayers by 19%. Emigration flows increase significantly in response, but only temporarily. Overall, the number of affected super-rich in the UK decreases by 0.26% for a 1% decline in the net-of-tax rate. Those who remain UK-resident increase reported income and income tax by around 50%, driven by foreign income coming into scope of UK tax, rather than investments being onshored. Emigrants induced to leave by the reform pay substantially less tax, but more than half still report non-zero UK income three years after leaving. By contrast, emigrants unaffected by tax changes retain a much smaller economic and fiscal footprint in the UK.

Award: IIPF Young Economists Award 2023

Other materials: policy brief, video explainer, op-ed in New Statesman and Advantage (CAGE magazine)

Media coverage: BBC, BBC News, BBC Radio 5 Live, BBC The Context, Bloomberg, Fairness Foundation, Financial Times (1), Financial Times (2), Guardian (1), Guardian (2), Guardian (3), Guardian (4), Guardian (5), Independent, New Statesman (1), New Statesman (2), Resolution Foundation, SRF, Sun, Tax Notes, Tax Policy Associates, Telegraph, The Times, Washington Post

Saving Responses to Mandatory Pension Plans
Working Paper, 2025.

To boost retirement savings, half of OECD countries mandate workers to contribute a portion of their earnings to pension accounts. I study saving responses to such mandates drawing on detailed administrative tax data from Switzerland. Leveraging a discontinuity in mandatory pension contributions at an earnings threshold, I present three main findings. First, the mandate has no effect on total savings, with an estimated crowd-out rate of 93%. Second, decomposing the saving response by asset type, I find that workers fully offset mandatory pension contributions by reducing private savings, primarily in financial assets. Third, I provide suggestive evidence that the mandate does increase total savings among workers who face liquidity constraints.

Supersedes “Behavioral Responses to a Pension Savings Mandate: Quasi-experimental Evidence from Swiss Tax Data”

The UK’s Global Economic Elite: A Sociological Analysis Using Tax Data
with Arun Advani, Mike Savage & Andy Summers, CAGE Working Paper 570, 2022.

We show the importance of international ties amongst the UK’s global economic elite, by exploiting administrative data derived from tax records. We show how this data can be used to shed light on the kind of transnational dynamics which have long been hypothesised to be of major significance in the UK, but which have previously proved intractable to systematic study. Our work reveals the enduring and distinctive influence of long-term imperial forces, especially to the former ‘white settler’ ex-dominions which have been called the ‘anglosphere’. These are allied to more recent currents associated with European integration and the rise of Asian economic power. Here there are especially strong ties to the ‘old EU-6’ nations of France, Germany, Netherlands, Belgium, Luxembourg, and Italy. The incredible detail and universal coverage of our data means that we can study those at the very top with a level of granularity that would be impossible using traditional survey sources. We find compelling support for the public perception that non-doms are disproportionately highly affluent individuals who can be viewed as a part of a global elite. However, whilst there is some evidence for the stereotype of the global wealthy parking themselves in the UK, this underplays the significance of the working rich. Our analysis also reveals the remarkable concentration of non-doms in central areas of London.

Other materials: policy brief, video explainer, data for the charts

Media coverage: BBC, BBC Newsnight, Bloomberg, Channel 4, Daily Mail, Economist, Everyday Society, Financial Times (1), Financial Times (2), Guardian (1), Guardian (2), Guardian (3), Independent, Indian Express, Mirror, New Statesman, Resolution Foundation, Reuters, Sydney Morning Herald, The Times (1), The Times (2), Washington Post, Les Echos, Frankfurter Allgemeine Zeitung

The Costs of Administering a Wealth Tax
Fiscal Studies, 42 (3-4), 677–697, 2021.

I assess the costs of administering a wealth tax for taxpayers and the tax authority in the UK context, based on evidence from existing UK taxes on wealth and comprehensive wealth taxes that have been imposed in other countries. My central estimate is that a well-designed wealth tax generates costs to taxpayers of 0.1 per cent of taxable wealth and costs to the tax authority of 0.05 per cent of taxable wealth. I discuss how these costs depend on design choices. My findings can inform revenue modelling and help to evaluate the desirability of wealth taxes.