The Basic Structure of Core-Satellite Strategy
The core-satellite strategy divides a portfolio into two layers: the "core" and the "satellite." The core portion accounts for 70-80% of the portfolio and consists of low-cost index funds and bonds, aiming to capture the market's average return reliably. The satellite portion makes up the remaining 20-30% and holds assets targeting higher returns, such as individual stocks, sector ETFs, and emerging market funds.
The advantage of this strategy is that the core secures market-average returns while the satellite pursues excess returns (alpha). Even if the satellite portion underperforms expectations, the core provides stable returns, preventing the overall portfolio from collapsing. It is a balanced approach that avoids both the risk of going fully active and the opportunity cost of committing entirely to index funds.
Building the Core - Owning the Entire Market at Low Cost
The standard approach for building the core is to center it on a global equity index fund (tracking MSCI ACWI or FTSE Global All Cap). A single fund provides diversified exposure to approximately 50 countries across developed and emerging markets, covering thousands of stocks, with expense ratios of just 0.05-0.15%. Depending on your risk tolerance, mixing in 10-30% of domestic or developed-market bond index funds can reduce overall portfolio volatility.
Rebalancing the core once or twice a year is sufficient. Books on global equity index investing cover regional allocation considerations and step-by-step rebalancing procedures.
Risk-Return Analysis by Core Ratio
Let's analyze the portfolio's risk-return characteristics at different core ratios. With 100% core (global equity index, expected return 6%, standard deviation 15%), the portfolio's expected return is 6% with a standard deviation of 15%. At 80% core / 20% satellite (satellite expected return 10%, standard deviation 25%), the expected return rises to 6.8% with a standard deviation of approximately 16.4%. At 60% core / 40% satellite, the expected return is 7.6% with a standard deviation of approximately 18.2%.
Doubling the satellite ratio from 20% to 40% increases expected return by only 0.8%, while standard deviation rises by 1.8%. Considering the return increase per unit of risk (the change in Sharpe ratio), a satellite ratio of 20-30% represents the efficient balance point. When the satellite ratio is too high, the core-satellite strategy loses its inherent advantage.
Pursuing Excess Returns with the Satellite Portion
In the satellite portion, concentrate on areas where you have knowledge or interest. If you're well-versed in technology, consider semiconductor-related ETFs; if real estate interests you, J-REITs; if you prefer dividend strategies, high-dividend stock ETFs. The key is to have a clear investment thesis for your satellite selections. Rather than "it seems like it might go up," base your choices on reasoning like "this sector has structural growth potential."
If the satellite portion underperforms, having the flexibility to increase the core ratio and return to simpler management is also important. Books on sector ETFs and thematic investing can help you explore a wide range of candidates for the satellite portion. Start by anchoring your core with index funds, then begin satellite investing within the bounds of your surplus capital.