Theme
For some time, the G20 has debated levying an annual minimum tax of 2% on the highest earners (billionaires). What would the effect of such a tax be? How could it be put into practice?
Summary
Wealth inequality has become one of the main problems facing modern societies due to its impact on social cohesion and economic stability. The number of people with net worth in excess of US$1 billion has grown at an annual rate of 10% in recent decades, rising from 140 people in the 1980s to 2,781 billionaires today. The increase has been accompanied by new ways of concealing wealth. Offshore tax evasion and the concealment of wealth in financial institutions headquartered in tax havens has been joined by investments in real estate, assets capable of sidestepping information exchange and maintaining secrecy, and the domiciles of major fortunes being moved to traditionally low-tax jurisdictions.
Empirical research confirms the tax deficit of people with substantial wealth. The greater part of a country’s population pays 25%-50% of its income in taxes across the entire range of incomes, whereas billionaires and multimillionaires pay 20%-25%. In all cases, the effective tax rates for billionaires are much lower than those for other income groups. In the absence of policies that address the billionaires’ tax deficit, this group’s wealth will continue rising and in 10 years’ time is on course to account for 20% of global GDP. Faced with this situation, various forums, particularly the G20, have been debating the levying of a global minimum tax on the highest income earners (multimillionaires and billionaires) as a necessary regulatory response. Such a tax would constitute a supplementary rate for billionaires equalling 2% of the value of their wealth.
In the past, attempts to levy a wealth tax in an effective manner have had limited success owing to the mobility of billionaires and the wealth itself. The coming into force of the FATCA Act in the US and the CRS in the OECD helped to establish the automatic exchange of information between tax authorities for certain financial assets. Broadening the information exchange to other asset classes could facilitate the implementation of a global minimum tax. Hammering out a multilateral agreement on a global minimum tax on billionaires’ wealth is an uncertain prospect, as negotiations between countries on common international standards tend to last for years. Even so, recent experience shows that agreements can be successfully sealed when multiple countries form a critical mass, take the first step unilaterally, sign a treaty and start to exchange information. Apart from the automatic exchange of information, the creation of a global assets register could become the governments’ ultimate goal in the years ahead, once the tax has been implemented.
Analysis
1. Introduction
The taxation of billionaire wealth has emerged as a prominent topic in global economic discussions. Over the past decades, the wealthiest 1% of households have held about 40% of global wealth, a share that has remained largely unchanged. A key reason for its persistence has been the ability of billionaires to pay lower effective tax rates compared with the rest of the population. In light of recent debates at the G20 summit in 2024, the global economic community has begun considering a new approach: implementing a 2% annual minimum tax on billionaire wealth.
This paper examines the dynamics of billionaire wealth accumulation and quantifies the revenue that could be generated from such a tax. Using billionaire wealth growth in the past decade, we estimate that annual global revenue could reach 0.22% of global GDP in 2025 and increase to 0.27% by 2030, from 0.06% today. The total revenue over the next seven years will be around US$2.1 trillion in absolute value. This can become a substantial income source for countries that could serve as a lever to effectively address future fiscal challenges and reduce inequality. In the sections below we explore the evolution of billionaire wealth over the past four decades and the mechanisms through which tax evasion is facilitated, we present annual revenue estimates from a global minimum tax and, finally, we discuss how global cooperation could effectively enforce this.
2. Global top wealth
Wealth inequality has emerged as one of the most important issues facing our modern societies, impacting social cohesion and economic stability. Since the 1970s the disparities in wealth between rich and poor have been aggravated by globalisation, technological progress and policy decisions that favoured the wealthy and large multinationals.[1] According to Forbes, there are today 2,781 individuals with an estimated wealth above US$1 billion. Compared with the global population they form only a tiny group, yet they concentrate an aggregate amount of US$14.2 trillion in wealth. The number of billionaires has grown at an average annual rate of 10% in the past decades, from 140 billionaires in the 1980s to 2,781 today (see Figure 1).
Figure 1. Number of billionaires, 1987-2024
To enable a comparison over the years, the increase of billionaire wealth can be calculated in income shares: the amount of global wealth held by top income earners (Atkinson et al., 2011). Using this method, billionaires account for the top 0.0001% of individuals globally. As shown in Figure 2, the wealth held as a percentage of global GDP has increased from 3% to 13.5%, over the past four decades. Figure 3 presents shows the extent of this increase using real compound annual growth rates of wealth (after correcting for world inflation). Every decade since the 1980s has seen the real wealth held by billionaires increase by around 7% annually, while in comparison the average wealth per adult has grown by 1.8%. Intuitively, the world’s wealthiest have experienced quadruple growth rates in wealth compared with the average adult. The compound effect of this increase has enormous implications for inequality and can explain the increase of global wealth shares held by the top 0.0001%.
Figure 2. Wealth of the global top 0.0001% (as a % of world GDP), 1987-2024
Figure 3. Real annual growth rates: wealth of top 0.0001% and average wealth per adult
| Years | Wealth of top 0.00001% | Average wealth per adult |
|---|---|---|
| 1987-1994 | 7,2 | 0,4 |
| 1994-2004 | 7,8 | 2,5 |
| 2004-2014 | 6,6 | 0,4 |
| 2014-2024 | 6,9 | 3,5 |
| Total | 7,1 | 1,8 |
Geographical variation across continents is another defining characteristic of billionaires’ global wealth. In 2024 the vast majority of billionaires resided in Asia, North America and Europe (2,545 out of 2,781), whilst smaller numbers resided in Oceania, the Middle East, Latin America and the Caribbean, and in Africa (see Figure 2). In terms of wealth, North America tops the list; the billionaires’ total worth was US$6 trillion out of the US$14.2 world total, equivalent to a particularly large 20% of North American GDP in 2024. The last column of Figure 3 presents similar percentages for all regions, indicating a significant variation of wealth ownership across the globe, with wealth appearing to have been amassed in the Global North and to be considerably lacking from the Global South.
Overall, the past four decades of billionaires’ wealth dynamics indicate that: (a) the share of wealth held by the top 0.0001%, equivalent to the global billionaires percentage, has increased considerably from 3% to 13.5% of global GDP; (b) the compound annual growth rate of wealth is four times the growth rate of the average individual, with the total effect of the difference having a profound impact on inequalities; and (c) there is a significant regional variation with more global billionaire wealth held at the Global North and less at the Global South.
Figure 4. Billionaire breakdown by region in 2024
| Region | Number of Billionnaires | Wealth (US$ bn) | GDP (US$ bn) | % Wealth / GDP |
|---|---|---|---|---|
| North America | 880 | 6015,5 | 30080 | 20 |
| Europe | 677 | 3444,7 | 24843,9 | 13.9 |
| Oceania | 52 | 230,4 | 2135,5 | 10.8 |
| Asia | 988 | 3705,3 | 39518,1 | 9.4 |
| Latin America and the Caribbean | 113 | 537 | 6126,2 | 8.8 |
| Middle East | 50 | 185,8 | 3492,6 | 5.3 |
| Africa | 21 | 90,9 | 3240,2 | 2.8 |
| Total | 2781 | 14209,6 | 109436,5 | 13 |
3. Billionaire mobility
3.1. Mobility of wealth
One of the ways of concealing wealth has been through shifting financial wealth to offshore destinations. Recent estimates show that US$12 trillion of global financial wealth is held today in tax havens, or around 12% of global GDP (Alstadsæter et al., 2023). This form of offshore tax evasion has a non-trivial effect at the very top of wealth distribution. Its practice is highly concentrated at the top 0.1% of richest households, which own around 80% of offshore wealth, while the top 0.01% own around 50% (Alstadsæter et al., 2018). The top 0.01% evade around 25% of their taxes by exploiting legal loopholes and exploiting tax havens (Alstadsæter et al. 2019).
In the past the most common form of secrecy took place through financial institutions based in tax havens. However, important policy developments in the last decade curtailed this practice significantly. In 2010 the US enacted the Foreign Account Tax Compliance Act (FATCA), requiring all banks to report account holdings of US citizens worldwide. A similar set of laws was introduced in 2014 by more than 100 countries known as the Common Reporting Standard (CRS). Financial institutions report account holdings, whilst tax administrations exchange this information automatically between them. Increased cooperation has led to a reduction of unreported financial wealth: after the introduction of the automatic exchange of information, it is estimated that around 70% of global offshore wealth is now being taxed, from an estimated 10% before the reforms (Alstadsæter et al., 2023).
Following the introduction of the CRS, high net-worth individuals have been using other asset classes to hide wealth. Evidence emerging from recent research has noted the use of real estate as an asset class to avoid information exchange and maintain secrecy. Quasi-experimental findings document an increase in UK real estate by US$45 billion following the introduction of CRS (Bomare & Le Guern Herry, 2022). Evidence from the Dubai property market suggests that foreign nationals hold around 43% of the total value of all residential property in the city, whilst a substantial boom in Russian investments in the city is documented following the invasion of Ukraine, with both utility accounts and residential leases associated with Russian nationals increasing sharply (Alstadsæter et al., 2024). This serves as evidence of the mobility of wealth. The latest information on offshore real estate can be found at the EU Tax Observatory’s Atlas of Offshore Wealth (Alstadsæter et al., 2022), which documents the global size of this harmful practice.[2]
3.2. Mobility of individuals
Hiding wealth in tax havens also takes place through the mobility of billionaires to other countries or regions. Figure 5 plots the percentage of billionaires residing outside their country (dark blue line) or region (light blue line) of nationality. This percentage has been increasing over the years. Around 9% are currently living in another country. Figure 6 shows the residency jurisdiction breakdown of billionaires living outside their country of nationality. Over the period from 2002 to 2024, out of all billionaires living outside their nationality country, 22.9% lived in Switzerland, 22.5% in the UK and 13.1% in the US. Other traditionally low-tax jurisdictions hold a particularly high percentage compared with their population: Hong Kong, Monaco, Singapore and the UAE. The list of countries is not surprising given the favourable regimes prevailing in these jurisdictions.
Figure 5. Billionaires residing in another country/region
Countries have been competing in attracting high net-worth individuals in a variety of ways (Agrawal et al., 2020; Baselgia & Martinez, 2024; Advani et al., 2023; Jakobsen et al., 2024). The introduction of preferential regimes have focused on: (a) preferential taxation of worldwide income if the tax residency is shifted; (b) tax reductions for a specific occupational activity, such as for athletes, artists and digital nomads; (c) regimes targeting retirees; and (d) citizenship or passport or preferential taxation in exchange for investment in the country. A number of such regimes in Europe and the upward trend since the 1990s have been documented in Flamant et al. (2021).
Figure 6. Residency jurisdiction of billionaires living outside their nationality countries, 2002-24
| Residency jurisdiction | % Billionaires |
|---|---|
| Switzerland | 22,9 |
| United Kingdom | 22,5 |
| United States | 13,1 |
| China | 7,6 |
| Hong Kong | 6,1 |
| Monaco | 5,6 |
| Singapore | 5 |
| United Arab Emirates | 5 |
| Other | 12,2 |
4. Taxing billionaires
For a long time, estimating how much billionaires evade in taxes was not possible due to the lack of data. One would need an estimate of their global income, an assessment of the fragmentation of their wealth, taking into account any avoidance practices, and a comparison against the taxes they pay. In recent years, a number of studies have begun addressing this gap in the US, in France, in Italy and in the Netherlands (Sáez & Zucman, 2019; Bach et al., 2023; Bruil et al., 2022; Guzzardi et al., 2023), while similar studies are ongoing in a number of countries.
Figure 7. The tax deficit of billionaires
By combining evidence from the studies with previous work on the effective tax rates of individuals across the income distribution we can assess the percentage of taxes paid in each percentile. A common plot for all four countries is shown in Figure 7. Individuals are binned in deciles based on their pre-tax income with a zoom in at the top of the income distribution, specifically at 0.1%, 0.01% and for billionaires.
What emerges from all four cases is a tax deficit for high net-worth individuals: the percentage of taxes over income falls dramatically at the very top. The majority of a country’s population pay 25%-50% of their income in taxes across the income distribution, while billionaires and centi-millionaires pay around 20%-25%. In all cases effective tax rates for billionaires are significantly lower than those for other income groups, and thus substantially lower than the average tax rate in the population. This indicates that the tax system is moderately progressive, except at the very top, where it becomes highly regressive.
Due to this tax deficit, the wealth of billionaires is expected to continue growing with a profound effect on inequalities. Figure 8 shows an extrapolation of their wealth as a percentage of global GDP up to 2050. Recall that this share has increased from 3% in 1987 to 14% today. In the absence of any policy to address the tax deficit of billionaires, we estimate that the wealth of billionaires will continue to increase to about 20% of global GDP in 10 years from now. A global minimum tax at the very top of the income distribution (billionaires and centi-millionaires) is emerging as a necessary policy response. Such a tax will act as a top-up tax for billionaires who pay less than the equivalent of 2% of their wealth value.
Figure 8. Projected wealth of the top 0.0001% as a percentage of global GDP
Figure 9 shows the revenue of a 2% minimum tax on billionaires’ wealth. The basis of projections is the growth of the number and wealth of billionaires in the past 10 years (5.9% and 9.9% respectively), which we can extrapolate for the years ahead.[3] The overall amount of additional revenue in 2025 amounts to 0.22% of global GDP, increasing to 0.27% in 2030, a significant increase from today’s 0.06%. Under current dynamics, the wealth of billionaires will increase from US$14.2 trillion in 2024 (around 13% of 2024 GDP) to around US$25 trillion in 2030 (around 20% of estimated 2030 GDP). The absolute amount of revenue to be collected until 2030 amounts to US$2.1 trillion, which can form a significant source of revenue for countries globally. This revenue can act as an important global lever for accelerating the green transition, enhancing investment in public services (health, education, infrastructure and entrepreneurship) and safeguarding the welfare state.
Figure 9. Projected revenues from a 2% minimum tax
| Year | Number of Billionaires | Wealth (as a % of GDP) | Taxes currently paid (as a % of GDP) | Revenues from minimum tax 2% (as a % of GDP) |
|---|---|---|---|---|
| 2025 | 2931 | 13,75 | 0,06 | 0,22 |
| 2026 | 3089 | 14,37 | 0,06 | 0,23 |
| 2027 | 3256 | 15,02 | 0,06 | 0,24 |
| 2028 | 3432 | 15,71 | 0,07 | 0,25 |
| 2029 | 3617 | 16,42 | 0,07 | 0,26 |
| 2030 | 3813 | 17,16 | 0,07 | 0,27 |
5. Implementation
In the past, attempts to tax wealth have been less successful due to the mobility of billionaires or the mobility of wealth, as described above. However, the introduction of FACTA in the US and the OECD’s CRS established automatic information exchange between tax authorities for certain financial assets. Currently financial institutions supply this information to national authorities. The latter exchange the information between them. Exchange happens for all individuals globally regardless of wealth, thus the information exists and is already being exchanged for billionaires. Extending the information exchange to other classes of assets can make a global minimum tax easier to implement.
The asset classes that must be exchanged are mainly company ownership information and real estate information. Regarding the former, the majority of countries worldwide operate a beneficial ownership register, which records the final beneficial owner of a company. This information is held by national governments, but the level of access varies from country to country. For high net-worth individuals, beneficial ownership information can be exchanged automatically, thus making it hard to structure wealth in shell companies, trusts and holding companies that conceal the ownership and income information of individuals. A second source of readily available information for automatic exchange is real estate. Most countries globally record property ownership, which can be exchanged automatically for billionaires based on asset allocation and country of residence.
Securing a multilateral agreement on a global minimum tax on billionaire’s wealth is uncertain, since negotiations between countries on common international standards take years. Yet recent experience has shown that countries can be successful in forging agreements if a critical mass of countries proceed unilaterally as a first step by exchanging information based on a newly established treaty. This approach would leverage existing national structures, with countries agreeing to enhance their data collection and sharing capabilities. Each country would retain control over its data but commit to exchanging relevant billionaire information with other treaty signatories. Such a decentralised method could be more flexible and quicker to implement, as it builds on existing frameworks and national policies. It can create a cascade effect with other countries joining to gain from the additional tax revenue.
Beyond the automatic exchange of information, establishing a global asset registry can be a final goal for governments in years to come and after the tax is established. The registry would have a centralised structure, where wealth information on billionaires would be collected and scrutinised. Billionaires would be required to supply all information through their accountants and countries would send existing data to this central entity, which would aggregate, cross-check and analyse the information. This approach ensures uniformity and consistency in data collection and management, facilitating comprehensive and accurate monitoring of billionaire wealth. By centralising the process, the global asset registry would provide a single, authoritative source of data on billionaire (or centi-millionaire) assets, enabling an efficient enforcement of the 2% global minimum tax.
Conclusions
Billionaire wealth has increased over the past four decades from 3% to 13.5% of global GDP. Novel findings from economic research have shown that billionaires benefit from considerably lower effective tax rates than the general population, with this growing wealth disparity aggravating global inequalities. The dynamics of wealth indicate that the share of wealth that billionaires have will continue to grow to around 20% of global GDP in the next decade, in the absence of any policy to address this. Introducing a 2% global minimum tax on billionaire wealth offers a viable solution to address these issues.
We estimate that such a tax can generate 0.22% of global GDP in additional revenue in 2025, while for the following years the revenue is projected to increase to 0.27% of global GDP by 2030. The overall amount generated from a tiny percentage of the world population can reach US$2.1 trillion cumulatively over the next seven years. This new source of revenue can become a catalyst for addressing future fiscal challenges and limiting the tax evasion practices that have allowed billionaires’ wealth to grow in the past. Recent discussions initiated at this year’s G20 summit in Brazil present a unique opportunity for countries to cooperate in order to tackle this important issue.
Bibliographical references
Advani, A., D. Burgherr & A. Summers (2023), Taxation and Migration by the Super-rich.
Agrawal, D.R., D. Foremny & C. Martı́nez-Toledano (2020), ‘Wealth tax mobility and tax coordination’, SSRN 3676031.
Alstadsæter, A., M. Collin, K. Mishra, A. Økland, B. Planterose & G. Zucman (2022), Towards a Global Real Estate Atlas: Offshore Real Estate in Selected Areas and Cities.
Alstadsæter, A., M. Collin, B. Planterose, G. Zucman & A. Økland (2024), Foreign Investment in the Dubai Housing Market, 2020-2024.
Alstadsæter, A., S. Godar, P. Nicolaides & G. Zucman (2023), Global Tax Evasion Report 2024, Eu-Tax Observatory.
Alstadsæter, A., N. Johannesen & G. Zucman (2018), ‘Who owns the wealth in tax havens? Macro evidence and implications for global inequality’, Journal of Public Economics, nr 162, p. 89-100.
Alstadsæter, A., N. Johannesen & G. Zucman (2019), ‘Tax evasion and inequality’, American Economic Review, vol. 109, nr 6, p. 2073-2103.
Atkinson, A.B., T. Piketty & E. Sáez (2011), ‘Top incomes in the long run of history’, Journal of Economic Literature, vol. 49, nr 1, p. 3-71.
Bach, L., A. Bozio, A. Gouillouzouic & C. Malgouyres (2023), ‘Quels impôts les milliardaires paient-ils ?’, Note de l’IPP, nr 92.
Baselgia, E., & I. Martínez (2024), Mobility Responses to Special Tax Regimes for the Super-Rich: Evidence from Switzerland.
Bomare, J., & S. Le Guern Herry (2022), Will We Ever be Able to Track Offshore Wealth? Evidence from the Offshore Real Estate Market in the UK.
Bozio, A., B. Garbinti, J. Goupille-Lebret, M. Guillot & T. Piketty (2023), ‘Predistribution vs redistribution: evidence from France and the US’, American Economic Journal: Applied Economics.
Bruil, A., C. Van Essen, W. Leenders, A. Lejour, J. Mohlmann & S. Rabaté (2022), ‘Inequality and redistribution in the Netherlands’, CPB Discussion Paper.
Chancel, L., T. Piketty, E. Sáez & G. Zucman (2022), World Inequality Report 2022, Harvard University Press.
Dharmapala, D., & J.R. Hines Jr (2009), ‘Which countries become tax havens?’, Journal of Public Economics, vol. 93, nrs 9-10, p. 1058-1068.
Flamant, E., S. Godar & G. Richard (2021), New Forms of Tax Competition in the European Union: An Empirical Investigation, Eu-Tax.
Freund, C., & S. Oliver (2016), The Origins of the Superrich: The Billionaire Characteristics Database, Working Papers 16-1, PIIE.
Guzzardi, D., E. Palagi, A. Roventini & A. Santoro (2023), ‘Reconstructing income inequality in Italy: new evidence and tax system implications from distributional national accounts’, Journal of the European Economic Association, vol 22, nr 5, p. 2180-2224.
Jakobsen, K., H. Kleven, J. Kolsrud, C. Landais & M. Muñoz (2024), ‘Taxing top wealth: migration responses and their aggregate economic implications’, Working Paper, nr 32153, National Bureau of Economic Research.
Langenmayr, D., & L. Zyska (2023), ‘Escaping the exchange of information: tax evasion via citizenship-by-investment’, Journal of Public Economics, nr 221, 104865.
Palan, R., R. Murphy & C. Chavagneux (2010), Tax Havens: How Globalization Really Works, Cornell University Press.
Piketty, T. (2014), Capital in the Twenty-first Century, Harvard University Press.
Sáez, E., & G. Zucman (2019), The Triumph of Injustice: How the Rich Dodge Taxes and How to Make Them Pay, W.W. Norton.
Tørsløv, T.R., L.S. Wier & G. Zucman (2022), ‘The missing profits of nations’, The Review of Economic Studies, vol. 90. nr 3, p. 1499-1534.
United Nations Population Division (2022), United Nations Database on Household Size and Composition 2022.
Zucman, G. (2013), ‘The missing wealth of nations: are Europe and the US net debtors or net creditors?, The Quarterly Journal of Economics, vol. 128, nr 3, p. 1321-1364.
Zucman, G. (2024), ‘A blueprint for a coordinated minimum effective taxation standard for ultra-high-net-worth individuals’, EU Tax Observatory.
Appendices
a. The Forbes billionaire data
We use the Forbes billionaire data to estimate the number and wealth of billionaire households in this paper. Forbes started publishing the data annually in 1987. It attempts to report individual billionaires and their wealth. In 2024 around 87.5% of reported billionaires are single individuals or married couples (with child dependents if any). However, in 12.5% of cases, Forbes is unable to identify the individual wealth of members of a family fortune and the family is reported together if they are worth a minimum of US$2 billion total or the equivalent of US$1 billion apiece. These combined family fortunes are listed with ‘& family’ (eg, ‘Bernard Arnault & family’) in the data. We assign these family fortunes to the head of the family (eg, Bernard Arnault), which leads to a minor underestimation of the number of billionaire households.
There are two notable inconsistencies in the Forbes data. First, Forbes has excluded all royal families and dictators, except in 1997 and 1998 when Forbes included eight monarchs and four dictators.[4] Secondly, all individual billionaires belonging to a family fortune were aggregated at the family fortune level from 1997 to 2000 (there was no attempt to assign wealth to individual billionaires as in other years). The number of billionaires is therefore systematically lower in these years.
Forbes does significant research to compile this data. It conducts interviews with the billionaire’s asset managers, financial advisors, rivals, peers and attorneys when possible. It also uses SEC documents, county filings, probate records and news articles to evaluate all asset types (eg, stakes in companies, real estate, art, yachts, planes, etc), while also considering their debts and charitable contributions. If a billionaire does not want to reveal the value of his private businesses, Forbes uses revenue or profit estimates combined with market ratios from similar public companies and applies a 10% liquidity discount. For venture-backed companies and businesses without recent equity sales, it adjusts valuations based on secondary market trading, input from ApeVue, Caplight and Notice.co, institutional investor holdings and sector performance since the latest funding round.
b. Estimating the real wealth of the top 0.0001% wealthiest households globally
We estimate the real wealth (corrected for inflation) of the top 0.0001% wealthiest households globally in two main steps. First, we estimate the number of households in the top 0.0001% of wealthiest households. Secondly, we estimate the share of wealth owned by billionaires within the top 0.0001% wealthiest households. We can then estimate the real wealth of the top 0.0001% wealthiest households since we observe the wealth of billionaire households in the Forbes data.
First, we estimate the number of households in the top 0.0001% of wealthiest households globally using the total global adult (ie, persons aged 25 or over) population. We use the total global adult population from the United Nations World Population Prospects 2022. The data is available for 1980 to 2021. We estimate 2022 to 2024 assuming a 1.5% growth rate of the adult population (ie, the mean growth rate of the adult population for the five years before 2022). We then assume that 80% of adults live together with one other adult (eg, are married, cohabit) to estimate the number of global households. For example, if there is a global adult population of 4 billion (about the global adult population in 2012), we assume that 80% of these adults (3.2 billion) live in the same household as one other adult (3.2/2 = 1.6 billion households) and the other 20% of adults live alone (0.8 billion adults = 0.8 billion households). Therefore, we would estimate that 4 billion adults reside in 2.4 billion households globally (1.6 + 0.8) and that the top 0.0001% households are composed of 2,400 households (2.4 billion/1 million).[5] In 2024 there were 4,883,332,860 world adults living in as estimated 2,929,999,716 households. There were therefore around 2,930 households in the top 0.0001% wealthiest households in 2024, which is close to the 2,781 billionaire households reported in the Forbes data.
Secondly, we estimate the share of wealth owned by billionaires (ρ) within the top 0.0001% wealthiest households using standard Pareto-interpolation techniques: ρ = (b / 0.0001)(a − 1) / a, where a is the Pareto coefficient (equal to about 1.3 to 1.4) and b is the fraction of global households who are US dollar billionaires. The value of b is calculated as the number of billionaire households (from the Forbes data) divided by the number of global households in the top 0.0001% of wealthiest households (estimated above). Throughout the full period, ρ is never greater than 1 (i.e., the wealth of global billionaire households never exceeds the wealth of the top 0.0001% wealthiest households). The wealth of the top 0.0001% wealthiest households globally is then obtained by dividing billionaire wealth by ρ. All wealth numbers are corrected for inflation and expressed in constant 2015 US$. We calculate an implicit price deflator by dividing world GDP (from the World Bank) in constant 2015 US$ by world GDP in current US$.
c. Residency and nationality
Our data on residency and nationality creates a record of the residency jurisdiction and nationality country of billionaires. We define a country as a political entity that can attribute a nationality. We use the jurisdictions in Forbes and in the academic tax haven literature.[7] Residency is defined as a permanent tax residency jurisdiction. A billionaire can only have one tax residency jurisdiction per year.
The data is constructed by using Forbes and conducting additional research on the billionaires living in a residency jurisdiction that does not correspond to their country nationality for any year. There are 4,871 billionaires from 2001 to 2024 according to Forbes. The latter reports one residency jurisdiction and one nationality jurisdiction per year for each billionaire. Forbes data do not account for billionaires who have multiple nationalities. We convert the citizenship jurisdiction to nationality as explained above. We then manually verify all billionaires (489) who do not have the same residency jurisdiction and nationality for any given year using Wikipedia, LinkedIn, Companies House and publicly available press articles, reports and court documents.
Identifying multiple nationalities requires an estimation strategy. It is not always possible to determine the exact year a nationality was acquired or abandoned.[8] We proceed as follows if several sources confirm that a billionaire possesses a given nationality, but there is no additional information on the exact acquisition year. First, the billionaire is assumed to have acquired the nationality at the age of 18 if he could have received the nationality during his childhood experiences (eg, being born or living in the country, parent’s nationality). Secondly, a billionaire is assumed to have received a nationality from a country with a citizenship-by-investment (CBI) programme during its first year.[9] Third, billionaires are assigned Israeli nationality at age 18.[10] Fourth, nationality is determined based on the number of years of residency if the residency year is identified and none of the above criteria apply.[11] Lastly, billionaires are considered to have abandoned their nationality if this is confirmed by several sources or if one of their nationality countries does not recognise additional nationalities.[12]
[1] For more information see the seminal study by Thomas Piketty (2022), Capital in the Twenty-First Century. Recent trends in inequality are presented in the World Inequality Report 2022.
[2] See https://atlas-offshore-world.org/.
[3] Growth over the past decade is the slowest of the last four decades and therefore represents the most conservative billionaire growth rate we could utilise.
[4] Royalty included Sultan Hassanal Bolkiah, Brunei; King Fahd bin Abdul Aziz Al Saud, Saudi Arabia; Sheikh Zayed bin Sultan Al Nahyan and Sheikh Maktoum bin Rashid Al Maktoum, United Arab Emirates; Queen Beatrix, the Netherlands; King Bhumibol Adulyadej, Thailand; Sheikh Jaber Al-ahmed Al-jabar Al-sabah and Sheikh Hamid bin Khalifa Al Thani, Qatar. Dictators included: the Suharto family, Indonesia; Hafez Al-Assad, Syria; Sadaam Hussein, Iraq; and Fidel Castro, Cuba.
[5] It is important to note that the assumption that 80% of adults worldwide live with one other adult and 20% live with no other adults could be refined. The number of adults living alone and the number of adults per household is difficult to estimate and vary significantly worldwide. Changing this assumption would have negligible effects on our results.
[6] The data were downloaded when the only years available were 1980 to 2022. We estimate 2023 and 2024 assuming a 3% growth rate of GDP (ie, the approximate mean growth rate of GDP for the 10 years before 2023). The World Bank recently released 2023 data and made minor modifications to its series. These modifications are negligible and do not affect our results.
[7] Members of different jurisdictions can therefore have the same nationality. Members of the Special Administrative Regions of China (ie, Hong Kong and Macao) are Chinese nationals. Members of the five inhabited Territories of the US are US nationals (ie, Guam, Puerto Rico, Northern Mariana Islands, US Virgin Islands and American Samoa). The same is true of the three British Crown Dependencies (ie, Guernsey, Jersey and the Isle of Man) and the members of the 11 inhabited British Overseas Territories (ie, Anguilla, Akrotiri and Dhekelia, Bermuda, British Virgin Islands, Cayman Islands, Falkland Islands, Gibraltar, Montserrat, Pitcairn Islands, St Helena, Ascension and Tristan da Cunha, and Turks and Caicos).
[8] Although there is significant public information on nationality, it is also likely that some additional nationalities are not identified. We believe that this is not a significant enough bias to have an impact on our data.
[9] Langenmayr & Zyska (2023) identify eight countries with high-risk CBI programmes. We assign the first year of the programme for St Kitts and Nevis (1984), Antigua and Barbuda (2013), Grenada (2014), Malta (2014), St Lucia (2016) and Vanuatu (2017). We assign the first year of the programme after a major reform that made the programme significantly more accessible for Cyprus (2013) and Dominica (2014).
[10] Jews, people with one or more Jewish grandparent and their spouses have the right to relocate to Israel and acquire Israeli nationality according to the 1950 Law of Return and the 1952 Citizenship Law. In practice, eligible people can apply online and pick up their passport upon arriving in Israel.
[11] We only determine the residency year nationality requirements for countries where we apply this rule. This includes the United Arab Emirates (no residency year requirement); Argentina (no requirement with family links and two otherwise); the US and the UK (three years with spouse national and five otherwise); Australia (four-five years depending on the time period); Canada (five years); Finland (four years with spouse national and five years otherwise); South Korea and Taiwan (three years with family links and five otherwise); the Seychelles and Monaco (10 years) and Switzerland (10-12 years depending on the time period). There are cases of billionaires obtaining the nationality of countries through accelerated procedures (eg, Pavel Durov and French nationality in 2021). These cases seem to be rare and covered extensively in the press, but it is possible that some of these accelerated nationality cases were not detected by our identification strategy.
[12] Examples of countries that do not recognise additional nationalities are China, Taiwan, India and Singapore.
