Don't Put It All in One Basket — The Basics of Diversification and Asset Allocation
One of the oldest maxims in investing is 'don't put all your eggs in one basket.' The point is to make sure that if you drop the basket, not every egg breaks at once. This simple analogy is the very heart of diversification. If you pour all your money into one stock, one asset, or one moment in time, you have no way to recover when it goes wrong. This article covers how to spread out risk, and how to understand its effect through numbers. (This is for reference only and is not a recommendation to buy or sell any specific product.)
Why Diversification Reduces Risk — The Magic of Correlation
The key to diversification lies in mixing 'assets that move differently from one another.' If assets A and B always swing in the same direction, mixing them leaves your risk unchanged — but if one rises while the other falls less, the overall volatility shrinks. For example, if in a given year stocks dropped -20% while bonds rose +5%, someone holding 50 stocks / 50 bonds would see a loss of only about -7.5%. Even when facing the same market shock, the turbulence they feel is reduced to about one-third.
The 3 Axes of Diversification: Asset, Region, and Time
- Asset diversification: Spread your money across assets with different characteristics — stocks, bonds, cash-equivalent assets (deposits/MMFs), and real assets (gold/REITs). The key is a combination that doesn't collapse together in a crisis.
- Regional diversification: If you keep 100% in domestic assets, you're fully exposed to shocks in Korea's economy and exchange rate. By mixing domestic and overseas (developed and emerging markets), a slump in one region can be offset by another.
- Time diversification: Instead of putting a lump sum in all at once, you reduce the risk of 'buying expensively in one go' by investing a fixed amount each month (installment/split purchasing). You end up buying more units when prices are low and fewer when they're high.
Asset Allocation by Example — If You Split 10 Million KRW
There is no single correct allocation. The principle, however, is to set your weightings according to your capacity to bear risk and your investment horizon. A commonly used rule of thumb is the simple formula 'stock weighting ≈ 100 − your age.' At age 40, that means roughly 60% stocks and 40% safe assets. This is just a starting point, not an absolute formula. Here is how 10 million KRW might be split by investment style.
- Conservative: Deposits/bonds 70% (7 million KRW) + equity 30% (3 million KRW) — for those who most dislike fluctuations in principal
- Balanced: Deposits/bonds 50% (5 million KRW) + domestic and overseas stocks 50% (5 million KRW) — balancing volatility and returns
- Aggressive: Deposits/bonds 30% (3 million KRW) + domestic and overseas stocks 70% (7 million KRW) — for those with a long horizon who can endure declines
Don't Let Even Cash-Equivalent Assets Exceed 'One Basket'
Diversification applies not only to investment assets but also to deposits, your safety net. Korea's deposit protection limit is 50 million KRW per person in combined principal and interest at each financial institution (raised from the previous 50 million KRW to 100 million KRW starting September 2025). If you put 150 million KRW into a single bank all at once, the amount above the limit may fall outside protection — so spreading your deposits across several financial institutions is itself a form of diversification. The limit and effective date can change with policy, so check the latest standards before depositing.
Diversify Your Taxes Too, and Your Returns Change
'Which account you hold it in' matters as much as where you hold it. An ISA (Individual Savings Account) offers tax savings — for the standard type, net profits up to 2 million KRW are tax-exempt, with the excess taxed separately at 9.9%. Also, if you contribute up to 9 million KRW per year combining a pension savings account and an IRP, you receive a tax credit: 16.5% for total annual salaries of 55 million KRW or less, and 13.2% above that. Filling the full 9 million KRW gets you a refund of 1.485 million KRW per year in the 16.5% bracket, or 1.188 million KRW in the 13.2% bracket. Even with the same diversified portfolio, using tax-advantaged accounts makes your real returns noticeably better.
Even with Diversification, 'Time' Grows Compounding — The Rule of 72
Diversification is a device for lowering risk, but the engine that grows your assets is ultimately compounding and time. You can estimate the number of years it takes for your principal to double as '72 ÷ annual return' (the Rule of 72). At 6% per year, 72÷6 = 12 years; at 8% per year, 72÷8 = 9 years. Using diversification to lower volatility so you don't get scared and bail out midway is the most realistic way to keep this compounding clock running all the way to the end.
Diversification is not a technique to maximize returns; it's closer to insurance that keeps you surviving in the market until the very end.
Once a Year, Restore Your Weightings — Rebalancing
Even if you initially set things at 50 stocks / 50 bonds, the weightings drift over time. If stocks rise sharply, before you know it you're at 65 stocks / 35 bonds, leaving you with a far riskier portfolio than you intended. Rebalancing means selling off some of the risen stocks and buying more bonds to return to 50:50. This naturally creates the discipline of 'selling what's expensive and buying what's cheap.' It's usually run simply — adjusting once a year, or whenever a weighting drifts more than ±5%p from its target.
Diversification isn't flashy. Standing next to someone who piles everything into one stock chasing a jackpot, the diversified investor always sees somewhat dull returns. But when the market swings violently, the one who doesn't lose sleep, buys time to recover losses, and keeps compounding running to the end is usually the person who diversified. First decide your investment horizon and the loss you can bear, then split across the three axes of asset, region, and time, and review your weightings once a year. This article is intended to provide general information; actual investment decisions and responsibility rest with you.