In the Early Stages, Savings Rate Is Everything
When you are just starting to build wealth, how much you can invest each month (your savings rate) has an overwhelmingly larger impact on your asset balance than differences in investment returns. For example, investing 30,000 yen per month at 3% annual return versus 50,000 yen per month at 3% yields approximately 4.19 million yen and 6.99 million yen after 10 years, respectively. Same return rate, but the difference in contribution amount directly translates to a difference in assets.
Meanwhile, investing 30,000 yen per month at 3% versus 7% annual return produces approximately 4.19 million yen and 5.18 million yen after 10 years. Despite a 4-percentage-point difference in returns, the gap is only about 990,000 yen. Increasing your monthly investment by 20,000 yen has a bigger impact than boosting your return by 4 percentage points.
Savings Rate vs. Return Rate - A Numerical Comparison
Let's look more closely at assets after 5 years starting from zero. At 30,000 yen per month and 5% return: about 2.04 million yen. At 50,000 yen per month and 5%: about 3.40 million yen. At 30,000 yen per month and 10%: about 2.32 million yen. Increasing your savings by 67% (30,000 to 50,000 yen) increases assets by 67%, but doubling the return rate (5% to 10%) increases assets by only 14%.
This pattern is more pronounced the smaller your assets. For someone with 1 million yen, a 5% return generates 50,000 yen per year, but saving an extra 10,000 yen per month adds 120,000 yen per year. In the early stages of wealth building, focus on raising your savings rate by even 1% rather than agonizing over which fund to pick.
Target Savings Rates by Life Stage
Target savings rates (including investments) as a percentage of take-home pay vary by life stage. For single people in their 20s, aim for 20-30%; for families with children in their 30s, 10-20%; and for those in their 40s and beyond once education costs peak, 20-30%. If you are pursuing FIRE, a savings rate of 50% or more is typically required, but the first milestone is consistently maintaining 15%.
There are only two ways to raise your savings rate: increase income or reduce expenses. Reviewing fixed costs (rent, insurance, phone bills, subscriptions) delivers lasting results and should be your first priority. Cutting variable expenses takes a greater psychological toll, so optimize fixed costs first. Practical guides on improving your savings rate explain why cutting expenses is more effective for wealth building than increasing income.
When Returns Start to Outweigh Savings
Once your assets exceed around 10 million yen, investment returns begin to outweigh the impact of additional savings. A 5% return on 10 million yen generates 500,000 yen per year - equivalent to saving over 40,000 yen per month. At 30 million yen, that becomes 1.5 million yen per year, or 125,000 yen per month.
Focus on savings rate in the early stages, then shift attention to investment efficiency as your assets grow. This phased approach is the rational strategy. Specifically, once your assets exceed 10 times your annual savings, it becomes worthwhile to also focus on portfolio optimization and cost reduction. Introductory books on wealth building provide a comprehensive view of combining savings and investing to build assets.
Next Steps - Track and Improve Your Savings Rate
Start by tallying your take-home income and expenses for the past three months to calculate your current savings rate: (Take-home income - Expenses) / Take-home income x 100. Then identify fixed costs you can reduce. Switching to a budget mobile plan (saving about 5,000 yen per month), canceling unused subscriptions (2,000-5,000 yen), and reviewing insurance (5,000-10,000 yen) can easily free up 10,000-20,000 yen per month from fixed costs alone.
Channel the freed-up amount directly into increased NISA contributions, and your improved savings rate automatically accelerates wealth building. Try our simulator to see how increasing your monthly contribution affects your future asset balance.