How does Henley & Partners calculate millionaire migration and what methodological criticisms have been raised?
Executive summary
Henley & Partners’ Wealth Migration Report says it quantifies "millionaire migration" by combining New World Wealth estimates of private wealth with indicators of where high-net-worth individuals (HNWIs) say they work or are active — but the underlying data and application of the stated method have been heavily challenged by independent reviewers and press outlets [1] [2] [3]. Critics argue the report does not measure actual physical moves, appears to rely on opaque or inappropriate proxies (notably LinkedIn-style work-location signals), and in some independent forensic reviews the published numbers do not follow the stated methodology and may be fabricated or manually adjusted [4] [2] [5].
1. How Henley & Partners says it calculates millionaire migration
Henley & Partners presents its annual Wealth Migration Report as an analysis of net inflows and outflows of millionaires and other HNWIs derived from data compiled by New World Wealth and internal modelling that estimates numbers and wealth of millionaires by country and city [1]. The report frames its outputs as indicative trends in where wealth is moving, and Henley cautions the figures are not absolute and are intended to signal broader patterns rather than precise headcounts [1] [6].
2. The data inputs Henley publicly cites — and what they mean
Publicly, Henley attributes its estimates to New World Wealth’s private-wealth database and says the methodology draws on public and private sources; critics note that New World Wealth’s processes are not fully disclosed to Henley or the public, leaving core assumptions opaque [1] [5]. The Tax Justice Network and press reporting point out the report’s methodology states it mainly measures where millionaires say they work — using social-media and professional-profile signals — rather than legal residence or physical relocation, a distinction that undermines claims of an “exodus” [3] [4].
3. Forensic reviews and statistical red flags
Independent forensic and statistical checks by Tax Justice UK, TaxPolicy Associates and others found patterns inconsistent with the published methodology: stable ratios across wealth bands that should vary, numbers that appear not to be derived from liquid investable assets despite the report’s wording, and internal contradictions suggesting the stated method wasn’t applied or cannot practically be applied at scale [5] [7] [8]. Financial Times coverage highlighted specific concern over the use of LinkedIn-type data and the definition of "private wealth" driving headline figures [2].
4. Principal methodological criticisms
Major criticisms focus on three linked problems: (a) the report does not track physical migration or tax residency but proxies mobility with where HNWIs "work" online, (b) the wealth definition and data sourcing are opaque and include real estate rather than only liquid investable wealth despite some public wording, and (c) the authors appear to overweight or manually adjust figures for ultra-wealthy cohorts, producing headline-grabbing net flows that, when placed in context, amount to near-0% migration rates of the overall millionaire population [4] [5] [8].
5. Henley & Partners’ defense and the industry view
Henley has defended the report as indicative rather than literal, saying critics have politicised the data and that the figures were never meant to be cited as precise counts responding to specific tax changes; the firm has commissioned an independent review in response to scrutiny [6]. Industry commentators acknowledge the report’s marketing power — Henley’s business depends on narratives about wealthy mobility — and some warn the report over-focuses on headline wealthy movements while ignoring broader tax-base shifts [9] [10].
6. What this means for journalists, policymakers and readers
Given the opaque sourcing, acknowledged proxy measures (work-location signals) and independent findings that the stated methodology appears not to have been applied consistently, the Henley figures should be treated as indicative signals from a commercial firm with a clear commercial interest in migration narratives rather than as robust, peer-reviewed migration statistics; numerous watchdogs advise caution before linking these numbers to policy causation such as tax changes [5] [4] [6]. Independent academic literature and tax-policy reviews consistently find HNWI migration responses to tax are typically small, a context often missing from headlines driven by the Henley report [8] [4].