Starting at 25 vs. 35 - A Simulation

In investing, time is the most powerful weapon you have. Even with the same amount invested at the same rate of return, a 10-year difference in starting age produces a dramatic gap in final wealth. Let's compare investing 30,000 yen per month at 5% annual return from age 25 to 60 versus starting the same plan at age 35.

For more detail, books on the power of time and compounding will let you feel the overwhelming advantage of starting early through hard numbers.

  • Starting at 25 (35 years): Principal 12.6 million yen → Final amount approx. 34.21 million yen (gains approx. 21.61 million yen)
  • Starting at 35 (25 years): Principal 9 million yen → Final amount approx. 17.86 million yen (gains approx. 8.86 million yen)

Starting just 10 years earlier results in roughly 16.35 million yen more at age 60. The difference in principal is only 3.6 million yen, yet the difference in investment gains reaches approximately 12.75 million yen. This gap is the "power of time" in compounding.

The Opportunity Cost of a "Lost Decade"

How much would the person who started at 35 need to invest each month to match the age-60 balance of the person who started at 25 (approximately 34.21 million yen)? At 5% annual return over 25 years, the required monthly contribution is roughly 57,500 yen. In other words, making up for a 10-year late start requires nearly doubling the monthly investment.

This is the opportunity cost of a "lost decade." Time cannot be recovered, but money can be earned later. However, catching up later demands a significantly heavier burden, which is why starting early - even with small amounts - is overwhelmingly advantageous.

The Importance of Starting Small but Starting Now

Many people think "I don't have enough money to start investing yet." But even 5,000 yen per month from age 25 grows to approximately 5.7 million yen by age 60 (at 5% annual return). Meanwhile, starting at 35 with 10,000 yen per month yields about 5.95 million yen. Investing half the amount but starting 10 years earlier produces nearly the same result.

  • 5,000 yen/month × 35 years (starting at 25): Principal 2.1 million yen → approx. 5.7 million yen
  • 10,000 yen/month × 25 years (starting at 35): Principal 3 million yen → approx. 5.95 million yen
  • 10,000 yen/month × 35 years (starting at 25): Principal 4.2 million yen → approx. 11.4 million yen

The length of the investment period, not the size of each contribution, is what ultimately determines your final wealth. Rather than waiting for the perfect moment, starting now with a small amount is the best strategy.

Investment Strategy by Age

Your investment strategy should be adjusted according to your age and life stage. Here is a basic framework by age group.

  • 20s: Time is your greatest ally. You can afford to take risk, so set a high equity allocation (80 to 100%) and start contributing even small amounts.
  • 30s: Income typically rises. Gradually increase your contributions and make full use of the Tsumitate NISA allowance. Target an equity allocation of 70 to 90%.
  • 40s: The acceleration phase of wealth building. Continue investing surplus funds aggressively while preparing for rising expenses like education costs. Target an equity allocation of 60 to 80%.
  • 50s and beyond: Time to think about your exit strategy. Gradually reduce equity exposure and increase the share of bonds and cash to lower risk.

Use our simulator to enter your age, monthly contribution, and expected return to see your projected wealth. Once you see the numbers 10 or 20 years out, you will feel the value of starting today.

an age-specific investment strategy guide will help you see the right level of risk for your stage of life.