A 25-year-old investing $100/month for 10 years, then stopping, ends up with more than a 35-year-old investing $100/month for 30 years. That's not intuition; that's math. Time compounds; contributions can't catch up.
The classic worked example
Two investors, both assuming 7% annual returns:
- Investor A — starts at 25. Invests $200/month for 10 years, then stops. Total contributed: $24,000. Balance at 65: ~$286,000.
- Investor B — starts at 35. Invests $200/month for 30 years. Total contributed: $72,000 (3× as much). Balance at 65: ~$245,000.
A put in $48,000 less and ended with $40,000 more. The difference is 10 more years of compounding on the early dollars.
Why the early years matter disproportionately
Your first $10,000 invested at 25 at 7% doubles to $20k at 35, $40k at 45, $80k at 55, $160k at 65. Four doublings. The same $10,000 invested at 35 only gets three doublings. One doubling is literally half the final balance.
This is why "starting with nothing at 25" beats "starting with something at 35" for wealth building. The something you have at 35 isn't enough to overcome the lost doublings.
What to do about a late start
If you're past the ideal window, the levers are:
- Max contributions — 401(k), IRA, HSA. Use every tax-advantaged account.
- Extend the horizon — work longer, retire later. Every extra year matters.
- Higher returns carry more weight — but don't chase returns; risk-adjusted stock market is the reliable path.
- Income gains compound through savings rate — making more = saving more (if you don't lifestyle-creep it away).
Starting age, monthly contribution, rate, horizon. Compare "start now" vs "start later".