Don’t Put Everything in One Basket — The Basics of Diversification and Asset Allocation
One of the oldest sayings in investing is, “Don’t put all your eggs in one basket.” It means that even if you drop one basket, not all the eggs will break at once. This simple analogy is the essence of diversification. If you put all your money into one stock, one asset, or one point in time, there may be no path to recovery if that choice goes wrong. This article explains how to spread risk and how to understand the effect in numbers. (This is for reference only and is not a recommendation to buy or sell any specific product.)
| Section | Key summary |
|---|---|
| Introduction | This simple analogy is the essence of diversification |
| Why diversification reduces risk — the magic of correlation | The core of diversification is combining assets that move differently from one another |
| The 3 axes of diversification: asset, region, and time | The key is a mix that does not collapse together in a crisis |
| Asset allocation example — if you were dividing 10 million won | There is no single correct allocation |
| Keep cash-like assets out of a single basket too | Short key point |
| Diversifying taxes can change your returns | Where you hold an asset matters as much as what you hold |
| Even with diversification, time grows compounding — the Rule of 72 | At 6% per year, 72÷6=12 years; at 8% per year, 72÷8=9 years |
| Once a year, restore the original weights — rebalancing | Even if you start with stocks 50 and bonds 50, the weights drift over time |
Why diversification reduces risk — the magic of correlation
The core of diversification is combining assets that move differently from one another. If assets A and B always move in the same direction, combining them does not reduce risk. But if the other asset falls less when one rises, overall volatility becomes smaller. For example, if stocks fell -20% in a given year while bonds rose +5%, a person holding stocks 50 and bonds 50 would lose only about -7.5%. Even under the same market shock, the felt level of fluctuation is reduced to roughly one-third.
The 3 axes of diversification: asset, region, and time
- Asset diversification: spread money across assets with different characteristics, such as stocks, bonds, cash-like assets (deposits and MMFs), and real assets (gold and REITs). The key is a mix that does not collapse together in a crisis.
- Regional diversification: if you put 100% only into domestic assets, you are fully exposed to shocks from the Korean economy and exchange rates. Combining domestic and overseas assets (developed and emerging markets) can allow weakness in one region to be offset by another.
- Time diversification: instead of investing a lump sum all at once, use a regular installment approach, buying a fixed amount each month, to reduce the risk of “buying expensively all at once.” You buy more units when prices are low and fewer units when prices are high.
Asset allocation example — if you were dividing 10 million won
There is no single correct allocation. The principle is to set weights according to your ability to bear risk and your investment horizon. A commonly used rule of thumb is “stock allocation ≈ 100 − age.” For a 40-year-old, that would mean about 60% in stocks and about 40% in safer assets. This is only a starting point, not an absolute formula. If you divide 10 million won by investor type, it might look like this.
- Conservative: deposits and bonds 70% (7 million won) + equity funds 30% (3 million won) — for those who most dislike principal fluctuation
- Balanced: deposits and bonds 50% (5 million won) + domestic and overseas stocks 50% (5 million won) — balancing volatility and return
- Aggressive: deposits and bonds 30% (3 million won) + domestic and overseas stocks 70% (7 million won) — for those with a long horizon who can withstand declines
Keep cash-like assets out of a single basket too
Diversification applies not only to investment assets but also to deposits, which serve as a safety net. Korea’s deposit protection limit is currently based on a combined principal and interest amount of 100 million won per person, per financial institution. If you place 150 million won in the same bank at once, the amount above the limit may not be protected, so spreading deposits across multiple financial institutions is also a form of diversification. Limits and effective dates may change depending on policy, so check the latest standard before making a deposit.
Diversifying taxes can change your returns
Where you hold an asset matters as much as what you hold. For a standard ISA, net gains up to 2 million won are tax-exempt, and any excess is separately taxed at 9.9%, creating a tax-saving benefit. In addition, if you contribute up to 9 million won per year across pension savings and an IRP, you can receive a tax credit: 16.5% applies for total salary of 55 million won or less, and 13.2% applies above that. If you fill the 9 million won limit, you receive a refund of 1.485 million won in the 16.5% bracket and 1.188 million won in the 13.2% bracket. Even with the same diversified portfolio, using tax-advantaged accounts can noticeably improve actual returns.
Even with diversification, time grows compounding — the Rule of 72
Diversification is a tool for lowering risk, while the engine that grows assets is ultimately compounding and time. You can estimate the number of years it takes for principal to double with “72 ÷ annual return” (the Rule of 72). At 6% per year, 72÷6=12 years; at 8% per year, 72÷8=9 years. The most realistic way to keep this compounding clock running to the end is to reduce volatility through diversification so you do not panic and exit midway.
Once a year, restore the original weights — rebalancing
Even if you start with stocks 50 and bonds 50, the weights drift over time. If stocks rise sharply, you may suddenly have stocks 65 and bonds 35, making the portfolio far riskier than intended. Selling part of the risen stocks and buying more bonds to return to 50:50 is rebalancing. It naturally creates the discipline of “selling what has become expensive and buying what has become cheap.” A simple approach is to adjust once a year, or when weights move more than ±5 percentage points away from the target.
Diversification is not flashy. Next to someone aiming for a jackpot by concentrating in one stock, a diversified investor often sees returns that feel a little dull. But when markets shake sharply, the people who usually sleep better, buy time to recover losses, and keep compounding to the end are those who diversified. First define your investment horizon and tolerable loss range, divide across the three axes of asset, region, and time, then review the weights once a year. This article is intended to provide general information, and actual investment decisions and responsibility belong to you.