Investing 500 a month at an assumed 7% a year for 30 years ends at 588,032. Starting ten years later and investing the same amount until the same date ends at 255,203, which is 43.4% as much, from 120,000 paid in instead of 180,000.
The difference is the first ten years. Money invested earlier has longer to compound, and the growth it earns in those years goes on growing until the end.
The two starts side by side
Both end on the same date:
| Start | Years invested | Paid in | Worth at the end | Growth |
|---|---|---|---|---|
| Ten years earlier | 30 | 180,000 | 588,032 | 408,032 |
| Ten years later | 20 | 120,000 | 255,203 | 135,203 |
What the example leaves out
The 7% is an assumption, not a forecast, and it is the same every year here. Real returns vary, and the years in which the money happens to be invested change the result.