Correlation in Portfolio Diversification Singapore

Correlation in Portfolio Diversification Singapore

Diversification is often described as the only “free lunch” in investing — combining assets that don’t move together reduces portfolio risk without necessarily sacrificing return. The mathematical backbone of diversification is correlation: the degree to which two assets move in the same direction at the same time. This guide explains correlation for Singapore investors building multi-asset portfolios. Not financial advice.

Table of Contents

Contents — Click to expand
  1. What Is Correlation?
  2. How Correlation Affects Diversification
  3. Singapore Asset Correlations
  4. Building a Low-Correlation Singapore Portfolio
  5. Correlation During Market Crises
  6. Portfolio Building Tools
  7. Frequently Asked Questions

What Is Correlation?

Correlation measures the degree to which two assets move together, expressed as a coefficient between −1 and +1:

  • +1.0: Perfect positive correlation — both assets move in lockstep (e.g. two identical ETFs). No diversification benefit.
  • 0: No correlation — asset movements are completely independent. Maximum diversification benefit per unit of return.
  • −1.0: Perfect negative correlation — when one rises, the other falls by the same amount. Theoretically zero combined volatility (very rare in practice).

The lower the correlation between two assets, the greater the diversification benefit when combined in a portfolio.

How Correlation Affects Diversification

Adding a second asset to a portfolio reduces overall volatility only if the correlation is below +1. The mathematical relationship (from Modern Portfolio Theory) is:

Portfolio Variance = w₁²σ₁² + w₂²σ₂² + 2w₁w₂σ₁σ₂ρ₁₂

Where ρ₁₂ is the correlation between assets 1 and 2. When ρ = 0, the 2w₁w₂σ₁σ₂ρ term disappears — meaning zero correlation eliminates the interaction term entirely, substantially reducing portfolio variance. This is the mathematical reason diversification works.

Singapore Asset Correlations

Asset Pair Approx. Correlation Diversification Benefit
S-REITs vs STI (Singapore stocks) +0.6 to +0.8 Low — both are SGX equities
S-REITs vs Singapore bonds/T-bills −0.1 to +0.2 High — different asset class
SGX equities vs global equities (VWRA) +0.5 to +0.7 Moderate
Equities vs gold −0.1 to +0.2 High — classic diversifier
SGX equities vs CPF/SSB ~0 Very high — CPF is uncorrelated with markets
Industrial REITs vs Retail REITs +0.5 to +0.7 Low — same REIT sector dynamics

Approximate historical correlations. Correlations change over time and tend to converge toward +1 during severe market crises.

Building a Low-Correlation Singapore Portfolio

A practical low-correlation Singapore portfolio might combine:

  • Global equities (VWRA or CSPX) — long-term growth engine, moderate correlation to SGX
  • S-REITs or Singapore blue chips — local income, moderate correlation to global equities
  • T-bills / SSBs / Fixed deposits — near-zero correlation to equities, capital preservation
  • CPF SA/RA — fully uncorrelated guaranteed 4% return
  • Gold (5–10%) — negative to zero correlation with equities, crisis hedge

This combination reduces portfolio volatility below what any single asset class could achieve alone. See our Retirement Planning Calculator and Asset Allocation guide for help modelling a balanced portfolio.

Correlation During Market Crises

A well-known limitation of correlation-based diversification is that correlations tend to rise toward +1 during market crises. During the COVID-19 crash (March 2020) and the 2022 rate hike selloff, most equities — including S-REITs, STI stocks, and global ETFs — fell simultaneously. Only gold, government bonds, and cash-like instruments (T-bills, CPF) held their value.

This “correlation breakdown” during crises means diversification provides less protection exactly when you need it most. The solution is to maintain a genuine allocation to true safe-haven assets (CPF, T-bills, SSB, gold) rather than relying entirely on equity diversification.

Portfolio Building Tools

Use these Kopi Notes tools to model diversified Singapore portfolios:

Frequently Asked Questions

What is correlation in portfolio diversification?
Correlation measures how two assets move relative to each other, on a scale from −1 (move in opposite directions) to +1 (move together). Assets with low or negative correlation provide diversification benefits — combining them reduces overall portfolio volatility without proportionally reducing expected returns.
Are S-REITs good diversifiers against Singapore stocks?
Partially — S-REITs and Singapore equities (STI stocks) have moderate positive correlation (0.6–0.8) since both are SGX-listed assets influenced by Singapore economic conditions and sentiment. For true diversification, combine S-REITs with assets from different asset classes: bonds, T-bills, gold, or global equities.
What assets have low correlation with equities in Singapore?
Singapore T-bills, SSBs, fixed deposits, CPF, and gold historically have low or negative correlation with SGX equities. These assets preserved value during market crashes (COVID-19 March 2020, 2022 rate hike selloff) when equity portfolios fell sharply.
Does diversification always work?
Not always — during severe market crises, correlations between most equity assets converge toward +1 (everything falls together). This “correlation breakdown” limits diversification benefits precisely when investors need them most. True diversification requires allocations to genuine safe-haven assets like government bonds, CPF, or gold — not just holding multiple equity positions.
How many stocks or REITs do I need to be diversified?
Research suggests that 15–20 uncorrelated positions eliminate most idiosyncratic (stock-specific) risk, leaving mainly market risk. However, holding 15 S-REITs is less diversified than holding 5 S-REITs plus T-bills and global equities — because the 15 REITs are highly correlated with each other. Asset class diversification matters more than raw stock count.