$400k+ difference
Compound interest: real numbers
Starting to invest at 25 versus 35 produces a $400,000+ gap by age 65, even at the same monthly contribution and rate. Time is the most powerful variable in compound growth — more impactful than rate or amount. $10,000 invested at 7% for 30 years grows to $76,123, with most of that gain accruing in the final decade.
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04 · ideas- Starting at 25 vs 35 creates a $400k+ gap at 65
- $10,000 invested at 7% for 30 years = $76,123
- The last decade of a 30-year investment generates more than the first 20 years
- Time is the most powerful investment variable — more than rate or amount
Compound interest means your returns generate their own returns. A $10,000 investment at 7% earns $700 in year 1. In year 2, you earn 7% on $10,700 — not just the original $10,000. Over decades, this creates exponential rather than linear growth.
The Rule of 72: Divide 72 by your annual return to find how long it takes to double your money.- 7% return → doubles every ~10.3 years
- 10% return → doubles every ~7.2 years
- Starting at 25 → $1,315,000 at age 65
- Starting at 35 → $608,000 at age 65
- Difference: $707,000 — from just 10 extra years of contributions
The first 10 years generated more than the last 30 years combined, because money invested early has the most time to compound.