Why Portfolio Construction Matters
Selecting individual investments is only part of managing wealth effectively. Portfolio construction — the deliberate allocation of capital across asset classes, geographies, currencies, and investment structures — determines the overall risk and return characteristics of wealth. Research consistently shows that asset allocation (the mix between equities, bonds, alternatives, and cash) is responsible for a greater proportion of long-run return variability than individual security selection or market timing.
For internationally mobile HNW investors, portfolio construction involves additional dimensions absent from the domestic investor's framework: currency allocation, multi-jurisdiction tax optimisation, custodian diversification, and the practical mechanics of managing a portfolio spread across multiple structures and platforms.
Modern Portfolio Theory: The Foundation
Harry Markowitz's 1952 paper "Portfolio Selection" established the mathematical basis for diversification. The core insight is simple but powerful: the risk of a portfolio depends not just on the risk of its individual assets, but on the correlations between them. Two assets that are individually volatile can combine to form a portfolio with lower volatility, if they do not move in unison.
The efficient frontier is the set of portfolios that offer the highest expected return for each level of risk. Portfolios below the frontier are inefficient — the same return could be achieved with less risk, or the same risk level could achieve higher expected return.
In practice, constructing the theoretical efficient frontier requires estimating expected returns, variances, and correlations for all assets — estimates that are inherently uncertain and sensitive to the historical period used. The efficient frontier is therefore a guiding framework rather than a precise prescription.
The practical implications of MPT for portfolio construction are:
- Hold diversified exposure across multiple asset classes with low mutual correlations.
- Avoid concentration in any single asset, sector, or geography.
- Understand that adding an imperfect hedge (an asset with somewhat negative correlation) reduces portfolio risk even if the asset itself appears unattractive in isolation.
Asset Class Allocation: The Starting Point
A typical HNW international portfolio considers allocation across:
Global equities (40–70%): The growth engine of the portfolio. Broad geographic diversification across US, Europe, Asia, and emerging markets through index ETFs or carefully selected active managers.
Fixed income (10–30%): Provides income, capital preservation, and low-correlation diversification. Duration management (mixing short and medium duration) reduces interest rate sensitivity.
Alternatives (10–25%): Infrastructure, private equity, real assets, gold, and hedge funds add return streams with different drivers from listed equities and bonds.
Cash and near-cash (5–10%): Liquidity buffer for planned expenditure and tactical redeployment.
These ranges are starting points. An investor 5 years from retirement with low income and high drawdown needs will weight differently from a 40-year-old wealth-builder with stable employment income and a 25-year horizon.
Factor Investing: Systematic Return Drivers
Beyond broad asset class allocation, factor investing provides a framework for understanding the systematic drivers of equity returns. The main validated equity factors are:
Value: Stocks trading cheaply relative to fundamentals (P/E, P/B, EV/EBITDA) have historically outperformed growth stocks over long periods, though the value premium has been volatile and periods of underperformance can last years. The academic basis for value goes back to Fama and French (1992).
Quality: Companies with high and stable return on equity, low leverage, and stable earnings growth have historically delivered superior risk-adjusted returns. Quality has been particularly resilient during market downturns.
Low volatility: Counterintuitively, lower-volatility stocks have delivered better risk-adjusted (and sometimes absolute) returns than high-volatility stocks over long periods — violating the simple risk/return trade-off that theory predicts. The low volatility anomaly is attributed partly to institutional investor constraints and partly to investor preference for lottery-like returns.
Momentum: Stocks that have performed well over the past 6–12 months tend to continue outperforming in the short term. Momentum is one of the most robust and replicable factors but is subject to sharp reversals ("momentum crashes") in volatile markets.
Size: Smaller-cap companies have historically outperformed large caps over very long periods, partly reflecting higher risk and lower liquidity. This premium has been less consistent in recent decades.
Factor ETFs allow investors to implement deliberate factor tilts at relatively low cost (TERs typically 0.15–0.40% for single-factor ETFs, versus 0.05–0.10% for broad market ETFs). The core-satellite approach commonly uses broad market ETFs as the core and factor ETFs as satellite tilts.
Currency Allocation in Portfolio Construction
For internationally mobile investors, currency allocation is an explicit portfolio construction decision, not an afterthought.
Key principles:
- Reference currency: Identify the primary currency in which the investor plans spending over the next 5–10 years. This is often the currency of their country of residence, but may be the currency in which they plan to retire.
- Liability matching: Major future liabilities (school fees, property purchase, retirement income) should be partially matched with assets in the same currency. A Paris school fees liability in 5 years is best funded by euro-denominated assets.
- Deliberate unhedged exposures: Unhedged foreign currency positions within the portfolio provide diversification against the reference currency's weakness, but add currency volatility. The decision to hedge or not hedge should be deliberate.
- Portfolio-level currency view: At the aggregate level, the investor should know the approximate currency exposure of their total portfolio — if 80% of assets are in USD and the investor lives in the eurozone, they have a significant USD/EUR bet that should be understood and sized appropriately.
Building Across Multiple Custodians
HNW investors with diversified portfolios often hold assets with multiple custodians: an offshore investment bond with one insurer, equities with a brokerage platform, alternatives with a private equity manager, and property elsewhere. This multi-custodian structure is sensible from a diversification and regulatory protection standpoint, but creates portfolio management challenges:
- Consolidated reporting: Without consolidated reporting, the investor may not have a clear view of total risk exposures, currency allocation, or asset class weights. Private banks and wealth management platforms increasingly offer consolidated reporting that aggregates across custodians.
- Overlap and concentration: Without a portfolio-wide view, investors may inadvertently concentrate exposures — holding equity market risk across multiple "different" products.
- Rebalancing mechanics: Rebalancing across custodians is logistically more complex than rebalancing within a single account.
A master "portfolio map" — a simple summary of all positions, their asset class, currency, and custodian — is a practical tool for investors managing wealth across multiple structures.
The Efficient Portfolio in Practice
The theoretically optimal portfolio differs from the practically optimal portfolio because:
- Transaction and management costs are real
- Tax considerations favour certain structures and account types
- Liquidity needs constrain allocation to illiquid alternatives
- Investor psychology means a portfolio that cannot be maintained through market volatility is less useful than a sub-optimal portfolio that will actually be held
The practical implication is that a simpler portfolio — broad-market global equity ETF, global bond ETF, some real assets, modest alternatives — consistently held through market cycles and rebalanced regularly, outperforms the average complex, high-cost, actively managed portfolio that gets abandoned during volatility or erodes value through excessive costs.
For HNW investors, the addition of alternatives and tax-efficient structures (offshore bonds, appropriate holding vehicles) justifies some additional complexity — but only where the added complexity genuinely improves outcomes rather than merely creating activity.
This guide is for general information only and does not constitute regulated investment advice. The value of investments can fall as well as rise and you may get back less than you invest. Portfolio construction does not eliminate market risk. Past performance is not a guide to future returns. Tax treatment depends on individual circumstances and the laws of multiple jurisdictions, which may change. Always seek independent regulated advice before making investment decisions.
How Global Investments can help
Global Investments provides portfolio construction advice for internationally mobile HNW clients — from asset class allocation and factor strategy to multi-custodian management and currency framework. We help clients build coherent portfolios that reflect their actual circumstances, time horizon, and tax position, rather than generic model allocations designed for domestic investors. Contact us to discuss portfolio construction.
Frequently Asked Questions
What is modern portfolio theory and is it still relevant?
Modern Portfolio Theory (MPT), developed by Harry Markowitz in the 1950s, provides the mathematical framework for selecting a combination of assets that maximises expected return for a given level of risk, or minimises risk for a given level of return. The 'efficient frontier' is the set of optimal portfolios. MPT remains foundational to portfolio construction thinking, though its assumptions — normal return distributions, stable correlations, rational investors — are known to be imperfect. It provides a useful framework rather than a precise optimisation tool.
What is factor investing and how does it work?
Factor investing identifies systematic return drivers ('factors') that have historically delivered excess returns over a market benchmark across long periods. The main academically validated equity factors are value (cheap stocks outperform expensive), quality (profitable, stable companies outperform weaker ones), low volatility (lower-risk stocks provide better risk-adjusted returns), momentum (recent winners continue to outperform in the short term), and size (small caps outperform large caps). Factor ETFs provide systematic exposure to these tilts at relatively low cost.
How does currency risk affect portfolio correlations?
When an investor holds foreign-currency assets, returns in the investor's reference currency depend on both the underlying asset's performance and the currency movement. This can either reduce or amplify volatility, and changes correlation relationships. Two assets that are uncorrelated in local currency terms may become correlated once both are measured in the investor's reference currency if both are affected by the same currency moves. International investors need to model correlations on a reference-currency basis, not in local currency terms.
How complex should a portfolio be for an HNW individual investor?
Portfolio complexity should be proportionate to the investor's capital base, sophistication, and ability to monitor and rebalance effectively. A well-diversified global equity ETF plus a global bond ETF plus a small alternatives allocation can outperform a 20-fund portfolio after costs, if the costs and execution of the complex portfolio are poor. Complexity adds value when it provides genuine diversification or access to return streams not available more cheaply — not for the sake of appearing sophisticated.
What is the core-satellite approach to portfolio construction?
The core-satellite approach holds a large 'core' allocation (typically 60–80% of the portfolio) in low-cost, diversified index funds providing broad market exposure, while a smaller 'satellite' allocation (20–40%) makes targeted active or thematic bets — specific managers, factor tilts, alternatives, or thematic positions. The core provides market returns at minimal cost; the satellite provides the opportunity for differentiated returns. This pragmatically combines the evidence on passive investing (core) with selective active use where it adds value (satellite).
This guide is for general information only and does not constitute financial advice or a personal recommendation. The value of investments can fall as well as rise and you may get back less than you invest. Past performance is not a guide to future returns. Tax rules, investment regulations, and the availability of specific investment vehicles change — always verify current rules and seek advice from a qualified independent financial adviser before making any investment decisions.