An investment strategy of regularly investing a fixed amount of money into the same investment at set intervals. When prices are high, fewer units are purchased; when prices are low, more units are purchased, resulting in a smoothed average acquisition cost. This mechanical approach eliminates emotional decision-making and is well-suited for long-term wealth building.
How Dollar-Cost Averaging Works - A Numerical Simulation
Dollar-cost averaging involves investing a fixed amount (for example, 30,000 yen) into the same mutual fund every month. When the fund's net asset value is 10,000 yen, you purchase 3 units; when it is 15,000 yen, you purchase 2 units; when it is 7,500 yen, you purchase 4 units. Since fewer units are bought when prices are high and more when prices are low, the average acquisition cost is smoothed out over time.
Compared to lump-sum investing, a lump-sum approach yields higher returns in a consistently rising market. However, since no one can predict market direction, dollar-cost averaging offers a lower psychological barrier for beginning investors by eliminating the "when should I invest?" decision. It also pairs naturally with automatic monthly deductions from salary, making it the standard approach when combined with NISA's Tsumitate category or iDeCo.
Limitations and Practical Considerations of Dollar-Cost Averaging
Dollar-cost averaging is not a silver bullet. If you invest in an asset that declines continuously over the long term, the average acquisition cost will decrease, but the asset value itself shrinks, making losses unavoidable. This strategy works effectively only when investing in assets with expected long-term growth, such as a global equity index fund.
As a practical consideration, the investment amount should be set within a comfortable range. If you stop contributing during a market downturn, you forfeit the greatest benefit of dollar-cost averaging - buying more units at lower prices. The key to success is "continuing to invest steadily regardless of market declines," and the prerequisite for this is setting an amount that does not strain your daily life. The correct sequence is to first secure an emergency fund, then determine your contribution amount within the range of surplus funds.
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