Time and compounding

The main engine.

Why early beats large

Money invested at 25 has forty years to compound; the same amount at 45 has twenty. The first is worth several times the second at retirement, for identical effort.

Reinvested income is where much of the long-run return comes from.
The rule of 72 estimates doubling time: 72 divided by the annual return.

Horizon decides the plan

Money needed in three years should not sit in something that can halve. The same asset is reckless for one goal and appropriate for another.